chore: always run units jobs with step-level skips (#13326)

### 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.

Author: blakeli0

.github/workflows/ci.yaml

@@ -56,62 +56,71 @@ jobs:
   units:
     runs-on: ubuntu-latest
     needs: bulk-filter
-    if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
     strategy:
       fail-fast: false
       matrix:
         java: [11, 17, 21, 25]
     steps:
     - name: Get current week within the year
       id: date
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
       run: echo "::set-output name=week_of_year::$(date +'%W' --utc)"
     - uses: actions/checkout@v4
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
     - uses: actions/setup-java@v4
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
       with:
         distribution: temurin
         java-version: ${{matrix.java}}
     - run: java -version
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
     - uses: actions/cache@v4
       id: mvn-cache
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-unified-${{ steps.date.outputs.week_of_year }}
     - run: .kokoro/build.sh
-      if: ${{ needs.bulk-filter.outputs.src == 'true' || needs.bulk-filter.outputs.ci == 'true' }}
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' && (needs.bulk-filter.outputs.src == 'true' || needs.bulk-filter.outputs.ci == 'true') }}
       env:
         JOB_TYPE: test
         JOB_NAME: units-${{matrix.java}}
   units-8-runtime:
     runs-on: ubuntu-latest
     needs: bulk-filter
-    if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
     name: "units (8)"
     steps:
     - name: Get current week within the year
       id: date
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
       run: echo "::set-output name=week_of_year::$(date +'%W' --utc)"
     - uses: actions/checkout@v4
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
     - uses: actions/setup-java@v4
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
       with:
         java-version: 8
         distribution: temurin
     - name: "Set jvm system property environment variable for surefire plugin (unit tests)"
       # Maven surefire plugin (unit tests) allows us to specify JVM to run the tests.
       # https://maven.apache.org/surefire/maven-surefire-plugin/test-mojo.html#jvm
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
       run: echo "SUREFIRE_JVM_OPT=-Djvm=${JAVA_HOME}/bin/java" >> $GITHUB_ENV
       shell: bash    
     - uses: actions/setup-java@v4
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
       with:
         java-version: 11
         distribution: temurin
         cache: maven
     - uses: actions/cache@v4
       id: mvn-cache
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' }}
       with:
         path: ~/.m2/repository
         key: ${{ runner.os }}-maven-unified-${{ steps.date.outputs.week_of_year }}
     - run: .kokoro/build.sh
-      if: ${{ needs.bulk-filter.outputs.src == 'true' || needs.bulk-filter.outputs.ci == 'true' }}
+      if: ${{ needs.bulk-filter.outputs.runnable == 'true' && (needs.bulk-filter.outputs.src == 'true' || needs.bulk-filter.outputs.ci == 'true') }}
       shell: bash      
       env:
         JOB_TYPE: test