chore: always run units jobs with step-level skips

[blakeli0]

Description

This PR solves the issue where required checks units (11), units (17), units (21), units (25), and units (8) get stuck in a pending "stuck forever" state on GitHub.

For example, https://screenshot.googleplex.com/9bpNwWP7jParbuM

Root Cause

The units and units-8-runtime jobs in .github/workflows/ci.yaml are conditionally skipped using job-level if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}.
Because the entire job is skipped at the job-level, the matrix versions are not expanded, and status checks like units (11) are never reported to GitHub. When these checks are configured directly as required status checks in branch protection rules, PRs that skip the jobs (e.g., workflow-only PRs) are stuck forever.

Solution

We removed the job-level if: runnable == true conditional from both units and units-8-runtime jobs so they always start. Instead, we applied the if: runnable == true check to every individual step inside these jobs.
When a PR doesn't need to run these checks:

1. The jobs will still start and run.
2. All steps will skip instantly.
3. The jobs will finish successfully in 1–2 seconds, reporting success and satisfying GitHub's required status checks.

[gemini-code-assist]

Note

Gemini is unable to generate a review for this pull request due to the file types involved not being currently supported.

[lqiu96]

IIUC, this seems to be a limitation of the Github CI. The required status for the matrix jobs aren't reported because they're never run (though Github CI docs does say that skipped jobs are reported as a success). I guess just not for matrix jobs.

Might be another data point to try and move away from bulk jobs (needing to run all GAPIC unit tests).

[blakeli0]

this seems to be a limitation of the Github CI. The required status for the matrix jobs aren't reported because they're never run

Yes exactly.