Auto-sync service labels for MM and TPG

[melinath]

What kind of contribution is this issue about?

Other (specify in details)

Details

We currently use the issue-labeler to add service labels to PRs in MM and issues in TPG. Adding the labels automatically creates them with a grey color, but we actually want them to be yellow for consistency. We should:

• Add a new command to issue-labeler that syncs the list of labels and ensures they have the right color
• Add a workflow to MM and TPG that runs this command nightly
  • This workflow needs to check the repository name is as expected before running the job, so that it won't run on forked repositories. Similar to https://github.com/GoogleCloudPlatform/magic-modules/blob/37e4abb059553f92e3eb4960ec0a2188a3cef77a/.github/workflows/scheduled-pr-reminders.yml#L11

References

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