[scudo] Track maximum resident memory in cache (#219036)
Add tracking for the resident memory in MapAllocatorCache. Unreleased
cache entries where Time != 0 are assumed to be resident, while entries
that have passed through releaseOlderThan where Time == 0 have had their
physical pages discarded.
Tracking is performed by updating CurrentResidentBytes on store, remove,
and release operations, recoding the peak in maxResidentBytes and
reporting it in getStats.
