Mostly-Read Write Locks

Read-oriented (reentrant) read-write locks.

mutable struct MostlyReadWriteLock <: AbstractLock ... end

Drop-in replacement for ConcurrentUtils.ReadWriteLock which is optimized to be more efficient for many fast readers and rare slow writers. That is, code assumes that read locks are common and are held for a short time (in particular, spinning waiting for readers to release their lock is sensible) while write locks are uncommon and held for a long time (that is, waiting for a writer to release its lock via a proper mutex and a context switch is sensible).