Use mergequeue for dependabot auto merges (#3594)

Keeps the same auto-merge behavior (for `semver-minor` updates) but changes it to use our mergequeue.

This improves DX because it prevents dependabot merges from bypassing the queue and also means that sanity
tests for these PRs don't fail (they run with the correct env)

---

#### Does this PR need a docs update or release note?

- [ ] ✅ Yes, it's included
- [ ] 🕐 Yes, but in a later PR
- [ ] ⛔ No

#### Type of change

<!--- Please check the type of change your PR introduces: --->
- [ ] 🌻 Feature
- [ ] 🐛 Bugfix
- [ ] 🗺️ Documentation
- [ ] 🤖 Supportability/Tests
- [ ] 💻 CI/Deployment
- [ ] 🧹 Tech Debt/Cleanup

#### Issue(s)

<!-- Can reference multiple issues. Use one of the following "magic words" - "closes, fixes" to auto-close the Github issue. -->
* #3591 

#### Test Plan

<!-- How will this be tested prior to merging.-->
- [ ] 💪 Manual
- [ ] ⚡ Unit test
- [ ] 💚 E2E

.github/workflows/auto-merge.yml

@@ -1,3 +1,4 @@
+# See https://docs.github.com/en/code-security/dependabot/working-with-dependabot/automating-dependabot-with-github-actions#common-dependabot-automations
 name: auto-merge
 
 on:
@@ -5,11 +6,24 @@ on:
     paths-ignore:
       - "src/**" # prevent auto-merge for go dependencies
 
+permissions:
+  pull-requests: write
+
 jobs:
-  auto-merge:
+  auto-approve-label:
     runs-on: ubuntu-latest
+    if: ${{ github.actor == 'dependabot[bot]' }}
     steps:
-      - uses: actions/checkout@v3
-      - uses: ahmadnassri/action-dependabot-auto-merge@v2 # https://github.com/marketplace/actions/dependabot-auto-merge
+      - name: Dependabot metadata
+        id: metadata
+        uses: dependabot/fetch-metadata@v1
         with:
-          github-token: ${{ secrets.DEPENDABOT_TOKEN }}
+          github-token: "${{ secrets.GITHUB_TOKEN }}"
+      - name: Enable auto-merge for Dependabot PRs
+        if: ${{steps.metadata.outputs.update-type == 'version-update:semver-minor'}}
+        run: |
+          gh pr edit "$PR_URL" --add-label "mergequeue"
+          gh pr review --approve "$PR_URL"
+        env:
+          PR_URL: ${{github.event.pull_request.html_url}}
+          GITHUB_TOKEN: ${{secrets.GITHUB_TOKEN}}