Add observability around exclusive locks

Coming from the incident in production#17504. In that incident we were waiting for an exclusive lock to be released within a database transaction.

To be able to detect this sooner, we could add observability around the use of exclusive locks in requests and Sidekiq jobs.

Ideally we'd include the following fields in the logs for a finished request or Sidekiq job

• exclusive_lock_count
• exclusive_lock_wait_duration_s
• exclusive_lock_hold_duration_s