Extend the existing label synchronization system to handle P0 and P1
priority labels in addition to backport/* labels:
- Add P0/P1 label syncing between issues and PRs bidirectionally
- Automatically add 'force_on_cloud' label to PRs when P0/P1 labels
are present (either copied from issues or added directly)
The workflow now triggers on P0 and P1 label events in addition to
backport/* labels, ensuring priority labels are properly reflected
across the entire PR lifecycle.
Refs: https://github.com/scylladb/scylla-pkg/issues/5383Closesscylladb/scylladb#25604