ci: Wire fs_backend Python tests into CI

[albertoperdomo2]

Summary

Adds CI coverage for the CPU-safe subset of the llm-d fs backend Python tests. The root unit-test target now also runs a dedicated unit-test-fs-backend-cpu target, which collects all tests under kv_connectors/llmd_fs_backend/tests/cpu/, a directory reserved for tests that do not require CUDA, vLLM, NIXL, or compiled storage extensions. New CPU-safe tests can be added by dropping files into that directory.

The fs backend pytest harness now supports a no_cuda_required marker so CPU-safe tests can bypass the existing autouse CUDA setup/teardown while preserving CUDA requirements for the rest of the suite. Python test dependencies for this lightweight path are kept in kv_connectors/llmd_fs_backend/tests/requirements-cpu.txt, and CI installs them before running make unit-test.

Test

Validated with:

make unit-test-fs-backend-cpu

Related Issues

• Wire fs_backend Python tests into CI #572

[albertoperdomo2]

cc: @kfirtoledo this PR might help both the CI tests and the issue you mentioned in the storage events emission test file.

[albertoperdomo2]

cc: @yankay

[yankay]

Nice work!
Only One ask : make unit-test now implicitly needs Python deps — Go-only devs will hit ModuleNotFoundError locally. Could we wrap pytest in a venv like uds-tokenizer-install-deps (Makefile:115-135) does? Then it stays self-contained and the CI pip install step goes away.

Thanks @albertoperdomo2!