Metrics for client event loops

[sumitaneja]

Feature description

We configure separate event loops for clients. Any suggestion on how we can get metrics on number of pending tasks /in use threads for client loop.

Something similar to metrics for executor pool (like below). Is something similar available for client workers or can be provided?

executor_queued_tasks{name="io",} 0.0
executor_queued_tasks{name="scheduled",} 1.0

executor_pool_size_threads{name="io",} 8.0
executor_pool_size_threads