Move runtime libraries from iree/tools/ into runtime/. (#9084)

Progress on https://github.com/google/iree/issues/8955, follow-up to https://github.com/google/iree/pull/9077.

This moves runtime library code from `iree/tools/utils` to `runtime/src/iree/tools/utils/`. The 'utils' name is still unfortunate (preferably each file would have a better place), but we can address that further down the line.
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0a033d4..ea40f03 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -634,6 +634,7 @@
   add_subdirectory(compiler)
 endif()
 
+# tools/ can depend on compiler/ and runtime/
 add_subdirectory(iree/tools)
 
 if(IREE_BUILD_TRACY)
@@ -690,7 +691,7 @@
 add_subdirectory(build_tools/benchmarks)
 
 #-------------------------------------------------------------------------------
-# Transitional directories.
+# Transitional directories
 #-------------------------------------------------------------------------------
 
 # The runtime uses tools and targets from elsewhere in the tree in a way
@@ -698,6 +699,8 @@
 # many things into top-level APIs). This should resolve once we finish
 # relayering everything.
 add_subdirectory(runtime)
+
+# samples/ can depend on anything, so we include it last
 if(IREE_BUILD_SAMPLES)
   add_subdirectory(samples)
 endif()