[Jobs][Consolidation] Signal file for api restart

[cblmemo]

After enabling consolidation mode, user needs to restart the API server to:

1. get the job refresh deamon
2. get the correct number of API server executors (since this will not be the same for consolidation mode)

This PR adds a signal file to indicating this restart process and print out warnings for user to restart the api server.

Tested (run the relevant ones):

• Code formatting: install pre-commit (auto-check on commit) or bash format.sh
• Any manual or new tests for this PR (please specify below)
• All smoke tests: /smoke-test (CI) or pytest tests/test_smoke.py (local)
• Relevant individual tests: /smoke-test -k test_name (CI) or pytest tests/test_smoke.py::test_name (local)
• Backward compatibility: /quicktest-core (CI) or pytest tests/smoke_tests/test_backward_compat.py (local)

[cblmemo]

/smoke-test --managed-jobs
/quicktest-core

[cg505]

Thanks!
Can we add a smoke test checking that the warning gets printed?