Consider adding critical thread metrics for monitoring

Exposing metrics for critical process threads could improve monitoring and provide additional insight for performance trending.

For example, certain threads in master and in the tserver processes need to run periodically, if they do not, this is an indication that the process is likely unhealthy / having issues. Exposing the fact that the threads are running, progressing or had a successful completion of a task would improve monitoring capabilities Additionally, if the "run-time" was provided, this could be used to gauge relative health by trending the performance over time / across upgrades,....

This issue is to capture possible candidate threads / processes that would be beneficial to incorporate into metrics reporting.

The issue names no files, tests, or entry points. Begin by identifying the critical periodic threads in the master and tserver processes, then determine which running, progress, completion, and runtime signals would be useful as metrics. Done means the candidate metrics and their intended health-monitoring value are defined clearly enough for implementation.

Written by the indexing model from the issue text.