Measure and test the discrepancy between connections in connpoolstats and physical connections on Linux

Measure and test the discrepancy between connections in connpoolstats and physical connections.

Permutations of interest include:

• before and after failovers
• At steady state after a period of time
• With operations that use the TaskExecutor pools vs. old global pools

The expected output here is a change to our docs to describe what this discrepancy is on Linux.