Disable workflows still relying on GCP self-hosted runners. (#18526)

See https://github.com/iree-org/iree/issues/18238.

We've finished migrating most load bearing workflows to use a new
cluster of self-hosted runners. These workflows are still using GCP
runners and are disabled:

* `build_test_all_bazel`: this may work on the new cluster using the
existing `gcr.io/iree-oss/base-bleeding-edge` dockerfile, but it uses
some remote cache storage on GCP and I want to migrate that to
https://github.com/iree-org/base-docker-images/. Need to take some time
to install deps, evaluate build times with/without a remote cache, etc.
* `test_nvidia_t4`, `nvidiagpu_cuda`, `nvidiagpu_vulkan`: we'll try to
spin up some VMs in the new cluster / cloud project with similar GPUs.
That's a high priority for us, so maybe within a few weeks.

Additionally, these workflows are still enabled but we should find a
longer term solution for them:

* `linux_arm64_clang` this is still enabled in code... for now. We can
disable
https://github.com/iree-org/iree/actions/workflows/ci_linux_arm64_clang.yml
from the UI
* arm64 packages are also still enabled:
https://github.com/iree-org/iree/blob/cc891ba8e7da3a3ef1c8650a66af0aa53ceed06b/.github/workflows/build_package.yml#L46-L50
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 31cd87f..0a900e8 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -56,28 +56,29 @@
   # Jobs that build all of IREE "normally"
   ##############################################################################
 
-  build_test_all_bazel:
-    needs: setup
-    if: contains(fromJson(needs.setup.outputs.enabled-jobs), 'build_test_all_bazel')
-    runs-on:
-      - self-hosted # must come first
-      - runner-group=${{ needs.setup.outputs.runner-group }}
-      - environment=${{ needs.setup.outputs.runner-env }}
-      - cpu
-      - os-family=Linux
-    steps:
-      - name: "Checking out repository"
-        uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
-        with:
-          submodules: true
-      - name: "Building and testing with Bazel"
-        env:
-          IREE_WRITE_REMOTE_BAZEL_CACHE: ${{ needs.setup.outputs.write-caches }}
-        run: |
-          ./build_tools/github_actions/docker_run.sh \
-            --env "IREE_WRITE_REMOTE_BAZEL_CACHE=${IREE_WRITE_REMOTE_BAZEL_CACHE}" \
-            gcr.io/iree-oss/base-bleeding-edge@sha256:cf2e78194e64fd0166f4141317366261d7a62432b72e9a324cb8c2ff4e1a515a \
-            ./build_tools/bazel/build_test_all.sh
+  # TODO(#18238): migrate to new runner cluster
+  # build_test_all_bazel:
+  #   needs: setup
+  #   if: contains(fromJson(needs.setup.outputs.enabled-jobs), 'build_test_all_bazel')
+  #   runs-on:
+  #     - self-hosted # must come first
+  #     - runner-group=${{ needs.setup.outputs.runner-group }}
+  #     - environment=${{ needs.setup.outputs.runner-env }}
+  #     - cpu
+  #     - os-family=Linux
+  #   steps:
+  #     - name: "Checking out repository"
+  #       uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
+  #       with:
+  #         submodules: true
+  #     - name: "Building and testing with Bazel"
+  #       env:
+  #         IREE_WRITE_REMOTE_BAZEL_CACHE: ${{ needs.setup.outputs.write-caches }}
+  #       run: |
+  #         ./build_tools/github_actions/docker_run.sh \
+  #           --env "IREE_WRITE_REMOTE_BAZEL_CACHE=${IREE_WRITE_REMOTE_BAZEL_CACHE}" \
+  #           gcr.io/iree-oss/base-bleeding-edge@sha256:cf2e78194e64fd0166f4141317366261d7a62432b72e9a324cb8c2ff4e1a515a \
+  #           ./build_tools/bazel/build_test_all.sh
 
   ############################### Configurations ###############################
   # Jobs that build IREE in some non-default configuration
@@ -327,7 +328,7 @@
       - setup
 
       # Toolchains
-      - build_test_all_bazel
+      # - build_test_all_bazel  # Currently disabled.
 
       # Accelerators
       # - test_nvidia_a100
diff --git a/.github/workflows/ci_linux_arm64_clang.yml b/.github/workflows/ci_linux_arm64_clang.yml
index 5539a2c..3772279 100644
--- a/.github/workflows/ci_linux_arm64_clang.yml
+++ b/.github/workflows/ci_linux_arm64_clang.yml
@@ -24,8 +24,8 @@
   setup:
     uses: ./.github/workflows/setup.yml
 
-  # TODO: Switch to GitHub-hosted arm64 runners when available?
-  # TODO: Switch runs-on labels to use different (non-GCP) self-hosted runners?
+  # TODO(#18238): migrate to new runner cluster
+  #   Or switch to GitHub-hosted arm64 runners when available?
   linux_arm64_clang:
     needs: setup
     runs-on:
diff --git a/.github/workflows/pkgci.yml b/.github/workflows/pkgci.yml
index b96cc70..5c98cda 100644
--- a/.github/workflows/pkgci.yml
+++ b/.github/workflows/pkgci.yml
@@ -73,11 +73,12 @@
     if: contains(fromJson(needs.setup.outputs.enabled-jobs), 'test_amd_w7900')
     uses: ./.github/workflows/pkgci_test_amd_w7900.yml
 
-  test_nvidia_t4:
-    name: Test NVIDIA T4
-    needs: [setup, build_packages]
-    if: contains(fromJson(needs.setup.outputs.enabled-jobs), 'test_nvidia_t4')
-    uses: ./.github/workflows/pkgci_test_nvidia_t4.yml
+  # TODO(#18238): migrate to new runner cluster
+  # test_nvidia_t4:
+  #   name: Test NVIDIA T4
+  #   needs: [setup, build_packages]
+  #   if: contains(fromJson(needs.setup.outputs.enabled-jobs), 'test_nvidia_t4')
+  #   uses: ./.github/workflows/pkgci_test_nvidia_t4.yml
 
   test_android:
     name: Test Android
diff --git a/.github/workflows/pkgci_test_nvidia_t4.yml b/.github/workflows/pkgci_test_nvidia_t4.yml
index f8cbf0f..b59cb20 100644
--- a/.github/workflows/pkgci_test_nvidia_t4.yml
+++ b/.github/workflows/pkgci_test_nvidia_t4.yml
@@ -19,6 +19,7 @@
 
 jobs:
   test_t4:
+    # TODO(#18238): migrate to new runner cluster
     runs-on:
       - self-hosted # must come first
       - runner-group=${{ github.event_name == 'pull_request' && 'presubmit' || 'postsubmit' }}
diff --git a/.github/workflows/pkgci_test_onnx.yml b/.github/workflows/pkgci_test_onnx.yml
index 46b0085..1d6b890 100644
--- a/.github/workflows/pkgci_test_onnx.yml
+++ b/.github/workflows/pkgci_test_onnx.yml
@@ -42,24 +42,25 @@
             runs-on: nodai-amdgpu-w7900-x86-64
 
           # NVIDIA GPU
-          - name: nvidiagpu_cuda
-            config-file: onnx_ops_gpu_cuda.json
-            numprocesses: 4
-            runs-on:
-              - self-hosted # must come first
-              - runner-group=${{ github.event_name == 'pull_request' && 'presubmit' || 'postsubmit' }}
-              - environment=prod
-              - gpu # TODO(scotttodd): qualify further with vendor/model
-              - os-family=Linux
-          - name: nvidiagpu_vulkan
-            config-file: onnx_ops_gpu_vulkan.json
-            numprocesses: 4
-            runs-on:
-              - self-hosted # must come first
-              - runner-group=${{ github.event_name == 'pull_request' && 'presubmit' || 'postsubmit' }}
-              - environment=prod
-              - gpu # TODO(scotttodd): qualify further with vendor/model
-              - os-family=Linux
+          # TODO(#18238): migrate to new runner cluster
+          # - name: nvidiagpu_cuda
+          #   config-file: onnx_ops_gpu_cuda.json
+          #   numprocesses: 4
+          #   runs-on:
+          #     - self-hosted # must come first
+          #     - runner-group=${{ github.event_name == 'pull_request' && 'presubmit' || 'postsubmit' }}
+          #     - environment=prod
+          #     - gpu # TODO(scotttodd): qualify further with vendor/model
+          #     - os-family=Linux
+          # - name: nvidiagpu_vulkan
+          #   config-file: onnx_ops_gpu_vulkan.json
+          #   numprocesses: 4
+          #   runs-on:
+          #     - self-hosted # must come first
+          #     - runner-group=${{ github.event_name == 'pull_request' && 'presubmit' || 'postsubmit' }}
+          #     - environment=prod
+          #     - gpu # TODO(scotttodd): qualify further with vendor/model
+          #     - os-family=Linux
     env:
       PACKAGE_DOWNLOAD_DIR: ${{ github.workspace }}/.packages
       CONFIG_FILE_PATH: tests/external/iree-test-suites/onnx_ops/${{ matrix.config-file }}