Add workflow to enforce labels on PRs

[desertaxle]

Adds a workflow to ensure that PRs are tagged with a tag named in .github/release.yml. This will ensure that we can properly categorize PRs in auto-generated release notes.

Closes https://github.com/PrefectHQ/prefect/issues/14399

Example

Checklist

• [x] This pull request includes a label categorizing the change e.g. maintenance, fix, feature, enhancement, docs.
• [x] This pull request references any related issue by including "closes <link to issue>"
  • If no issue exists and your change is not a small fix, please create an issue first.
• [ ] If this pull request adds new functionality, it includes unit tests that cover the changes
• [ ] If this pull request removes docs files, it includes redirect settings in mint.json.
• [ ] If this pull request adds functions or classes, it includes helpful docstrings.