Automatic merge from submit-queue (batch tested with PRs 46033, 46122, 46053, 46018, 45981)

Log age of stats used for evictions during eviction tests

I recently added prometheus metrics for the age of the metrics used for evictions #43031.  It would be nice to surface these during eviction tests, so I can better assess how old stats are, and whether or not the age of stats causes extra evictions.

This isnt super-high priority, and can be done after code-freeze, since it is a testing improvement.  Feel free to take a look whenever either of you has time.

/assign @mtaufen 
/assign @Random-Liu