This commit reverts the triage workflow to restore the previous PR support using the `pull_request_target`, which is more secure as it doesn't allow fork repositories to change the workflow before it runs.
Additionally, this fixes an issue currently causing the workflow to break as cli/cli uses the `discuss` label but github/cli uses the `triage` label.
- replaces creating discussions for issues
- supports discussing both issues and pull requests
- populates more information about related issues and pull requests in triage issues
