Propagate feature flag actors in all RPC services

In gitlab!101218 (merged), we implemented the foundation to propagate feature flag actors to Gitaly via gRPC metadata. The change touched gRPC stubbing in GitLab rails. Any performance impact may yield global degrade. As a result, we were very defensive when rolling out:

• The new changes were behind feature flag actors_aware_gitaly_calls (gitlab#381516 (closed))
• The propagation is applied for Commit service only.

This issue is to track the progress of rolling out the new propagation mechanism to all gRPC services from Gitlab Rails side.