The Mutex destructor is needed only to clean up debug logging
and invariant checking synch events. These are not supposed
to be used in production, but the non-empty destructor has
costs for production builds.

Instead of removing synch events in destructor,
drop all of them if we accumulated too many.
For tests is should not matter (we maybe only consume
a bit more memory). Production builds should be either unaffected
(if don't use debug logging), or use periodic reset of all synch events.

PiperOrigin-RevId: 577106805
Change-Id: Icaaf7166b99afcd5dce92b4acd1be661fb72f10b