Branch protection blocks PRs that don't trigger e2e-tests workflow

[raballew]

Problem

PRs that don't touch e2e-relevant paths (e.g. workflow-only changes) get permanently blocked by branch protection.

The e2e.yaml workflow uses dorny/paths-filter to skip builds when only unrelated files change. But the e2e-tests job depends on the build jobs (needs: [build-controller-image, build-operator-image, build-python-wheels]), so when those are skipped, e2e-tests is also skipped by GitHub Actions. A skipped job never reports a status check. Since branch protection requires e2e-tests (ubuntu-24.04, amd64) and e2e-tests (ubuntu-24.04-arm, arm64), the PR sits in "Waiting for status to be reported" forever.

Currently affected:

• build(deps): bump astral-sh/ruff-action from 3.6.1 to 4.0.0 #552 (ruff-action bump -- only touches .github/workflows/lint.yaml)
• build(deps): bump actions/create-github-app-token from 2.2.1 to 3.1.1 #545 (create-github-app-token bump -- only touches .github/workflows/backport.yaml and .github/workflows/trigger-packages.yaml)

Any future PR that only modifies files outside the paths filter (controller/**, e2e/**, python/**, .github/workflows/e2e.yaml, Makefile) will hit the same issue.

Proposed solution

Add a gate job at the end of e2e.yaml that always runs, regardless of whether the actual test jobs were skipped:

e2e-result:
  if: always()
  needs: [e2e-tests, e2e-compat-old-controller, e2e-compat-old-client]
  runs-on: ubuntu-latest
  steps:
    - run: |
        if [[ "${{ contains(needs.*.result, 'failure') }}" == "true" ]]; then
          echo "E2E tests failed"
          exit 1
        fi
        echo "E2E tests passed or were skipped"

Then update branch protection rules to require e2e-result instead of the individual matrix job names (e2e-tests (ubuntu-24.04, amd64), e2e-tests (ubuntu-24.04-arm, arm64)).

This way:

• Paths match: build jobs run, e2e-tests run, gate reports their result
• Paths don't match: build jobs skip, e2e-tests skip, gate still runs and reports success

The same pattern should be evaluated for other conditional workflows (controller-tests, python-tests) if they have similar required checks.