Minor changes as per the review
Test for monitoring interval

Ensure checking the interval before returning the histogram
Record op time on the async code path
Check monitoring interval before getting histogram

Make sure that that if the interval is expired you return
a reset histogram and not the stale one.
Separate sync and async operation times
Track connection exception as a separate metric
Fixing NPE in during client pool shutdown
Refactoring RESTClientFactory and R2Store to accept a D2 client
Naming convention cleanup of R2Store