Adding mirror initiation label in mirror trigger makes more one PP processor to pickup the changes due to cooncurrency (when more than triggered almost same time.

Fix/Improve this by -

• Update mirror trigger workflow to NOT to add mirror initiation label
• Make the PR processor logic as
  • Get all the PRs which are not mirrored (take from last mirrored PR using timestamp greater than), leave the PRs which are in progress (with mirror initation label)
  • For each of above PR, add mirror initation label, process and add mirror completion label.

This will reduce and almost remove the concurrency issue