[RFC0010] Add shared ROCm test utility helpers

[jayhawk-commits]

Summary

Adds the first shared test utility module for RFC0010 runner cleanup.

• Add import-safe test_tools/test_utils.py with reusable helpers for:
  • test category normalization
  • AMDGPU/GFX architecture parsing and wildcard matching
  • GTest and CTest sharding argument/env construction
  • CTest label parsing and label include/exclude argument construction
  • rocminfo GPU architecture discovery with injectable subprocess runners
  • ASAN artifact-group detection without module-level environment reads
• Add focused unit tests under test_tools/tests/test_utils_test.py.
• Update the existing legacy unit_test_runner.py expectation for the current combined CTest -LE OR-regex behavior.

This PR deliberately does not rewire the legacy generic test_runner.py or project-owned runner scripts. It only establishes the shared helper surface and tests it in isolation.

Refs #3968.

Testing

• pre-commit run --files build_tools/github_actions/tests/unit_test_runner.py test_tools/test_utils.py test_tools/tests/test_utils_test.py
• python -m py_compile test_tools/test_utils.py test_tools/tests/test_utils_test.py build_tools/github_actions/tests/unit_test_runner.py
• python -m unittest discover -s test_tools/tests -p *_test.py
• python build_tools/github_actions/tests/unit_test_runner.py