Clean up GCS fork: minimal changeset vs upstream actions/cache

Realign the fork so it diffs from upstream actions/cache only by the GCS
cache backend, instead of carrying unrelated downgrades and deletions.

- Restore package.json/package-lock.json to upstream 5.0.4 deps; the fork
  had downgraded to 4.2.x. Re-add @google-cloud/storage (gcsCache.ts needs it).
- Rebuild dist/ against the restored deps so it bundles the real GCS client
  rather than a stale build against downgraded deps.
- Restore deleted upstream files: 7 workflow YAMLs, .github/CODEOWNERS,
  .licensed.yml. (To be disabled in the fork, not removed.)
- Revert action.yml/restore/save manifests to upstream name/description/
  author; keep only the gcs-bucket/gcs-path-prefix inputs as the fork diff.
- auto-tag.yml: track upstream's highest semver release tag, moving both the
  exact-version tag and the major alias, instead of force-pinning v1.
- Remove checkout/ composite action; relocated to Cula-Technologies/checkout.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.github/workflows/pr-opened-workflow.yml

@@ -0,0 +1,25 @@
+name: Assign pull request reviewer
+
+on:
+  pull_request_target:
+    types: [opened]
+
+permissions:
+  pull-requests: write
+
+jobs:
+  run-action:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Get current oncall
+        id: oncall
+        run: |
+          echo "CURRENT=$(curl --request GET 'https://api.pagerduty.com/oncalls?include[]=users&schedule_ids[]=P5VG2BX&earliest=true' --header 'Authorization: Token token=${{ secrets.PAGERDUTY_TOKEN }}' --header 'Accept: application/vnd.pagerduty+json;version=2' --header 'Content-Type: application/json' | jq -r '.oncalls[].user.name')" >> $GITHUB_OUTPUT
+
+      - name: Request Review
+        run: |
+          curl -X POST -H "Accept: application/vnd.github+json" -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN}}" https://api.github.com/repos/${{github.repository}}/pulls/${{ github.event.pull_request.number}}/requested_reviewers -d '{"reviewers":["${{steps.oncall.outputs.CURRENT}}"]}'
+
+      - name: Add Assignee
+        run: |
+          curl -X POST -H "Accept: application/vnd.github+json" -H "Authorization: Bearer ${{ secrets.GITHUB_TOKEN}}" https://api.github.com/repos/${{github.repository}}/issues/${{ github.event.pull_request.number}}/assignees -d '{"assignees":["${{steps.oncall.outputs.CURRENT}}"]}'