ci: pin containers to digest, enable more zizmor rules (#38779)

Enable more strict "pedantic" zizmor rules and fix issues. Service
containers are pinned to hash and renovate will update them. Enabled
rules:

- https://docs.zizmor.sh/audits/#excessive-permissions
- https://docs.zizmor.sh/audits/#unpinned-images
- https://docs.zizmor.sh/audits/#template-injection

---------

Signed-off-by: silverwind <me@silverwind.io>

.github/workflows/pull-labeler.yml

@@ -10,6 +10,8 @@ concurrency:
   group: ${{ github.workflow }}-${{ github.head_ref || github.run_id }}
   cancel-in-progress: true
 
+permissions: {}
+
 jobs:
   labeler:
     runs-on: ubuntu-latest