ci: Restrict benchmark uploads and comments to main and PRs with proper permissions

Author: talagrand

.github/workflows/benchmark.yml

@@ -37,9 +37,9 @@ jobs:
           output-file-path: output.txt
           github-token: ${{ secrets.GITHUB_TOKEN }}
           # Push and deploy GitHub pages branch automatically
-          auto-push: true
+          auto-push: ${{ github.ref == 'refs/heads/main' }}
           # Show alert with commit comment on detecting possible performance regression
           alert-threshold: '125%'
-          comment-on-alert: true
+          comment-on-alert: ${{ github.event_name != 'pull_request' || github.event.pull_request.head.repo.full_name == github.repository }}
           fail-on-alert: true
           alert-comment-cc-users: '@${{ github.actor }}'