Chore: Migrate workflows to use create-github-app-token (#2142)

- Removes dependabot.yml as renovate will update grafana-sdk for us
- Migrates to `create-github-app-token`
- Pin workflows
- Removes is-compatible.yml I found that workflow not helping much but
creating an annoyingly long comment

Fixes https://github.com/grafana/oss-big-tent-squad/issues/144

.github/workflows/stale.yml

@@ -11,7 +11,7 @@ jobs:
   stale:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@v9
+      - uses: actions/stale@5bef64f19d7facfb25b37b414482c7164d639639 # v9.1.0
         with:
           repo-token: ${{ secrets.GITHUB_TOKEN }}
           operations-per-run: 750