Fork CUDA and ROCm guides into separate pages. (#15196)

Fixes https://github.com/openxla/iree/issues/15115

These pages are very similar, but both stacks have undergone enough
development recently that they can now stand on their own. This PR
primarily forks the pages, but it also does some minor cleanup (fixing
dead links, adjusting formatting).

|  | |
|--------|--------|
| Current page |
https://www.iree.dev/guides/deployment-configurations/gpu-cuda-rocm/ |
| Preview of this PR - CUDA |
https://scotttodd.github.io/iree/guides/deployment-configurations/gpu-cuda
|
| Preview of this PR - ROCm |
https://scotttodd.github.io/iree/guides/deployment-configurations/gpu-rocm
|
diff --git a/docs/website/mkdocs.yml b/docs/website/mkdocs.yml
index bcdc071..ce2128b 100644
--- a/docs/website/mkdocs.yml
+++ b/docs/website/mkdocs.yml
@@ -133,7 +133,8 @@
           - CPU: "guides/deployment-configurations/cpu.md"
           - CPU - Bare-Metal: "guides/deployment-configurations/bare-metal.md"
           - GPU - Vulkan: "guides/deployment-configurations/gpu-vulkan.md"
-          - GPU - CUDA/ROCm: "guides/deployment-configurations/gpu-cuda-rocm.md"
+          - GPU - CUDA: "guides/deployment-configurations/gpu-cuda.md"
+          - GPU - ROCm: "guides/deployment-configurations/gpu-rocm.md"
           - GPU - Metal: "guides/deployment-configurations/gpu-metal.md"
       - "Other topics":
           - Developer tips and tricks: "guides/developer-tips.md"
@@ -201,7 +202,9 @@
         "deployment-configurations/cpu.md": "guides/deployment-configurations/cpu.md"
         "deployment-configurations/bare-metal.md": "guides/deployment-configurations/bare-metal.md"
         "deployment-configurations/gpu-vulkan.md": "guides/deployment-configurations/gpu-vulkan.md"
-        "deployment-configurations/gpu-cuda-rocm.md": "guides/deployment-configurations/gpu-cuda-rocm.md"
+        "deployment-configurations/gpu-cuda-rocm.md": "guides/deployment-configurations/gpu-cuda.md"
+        # The CUDA/ROCm page split into two pages
+        "guides/deployment-configurations/gpu-cuda-rocm.md": "guides/deployment-configurations/gpu-cuda.md"
 
         # "bindings/" moved under "reference/"
         "bindings/index.md": "reference/bindings/index.md"