The original code would immediately error out if a contended lock
acquisition were interrupted before it could acquire the lock.
This led to a behavioral difference from MRI, which does not raise
errors. It is not clear whether that's because locks in MRI can
never be truly contended (if the lock is not available the thread
is put to sleep and woken by the lock owner) or because they
explicitly try again to acquire the lock after waking.

In this version of the code, we opt to continue trying to acquire
the lock via a loop, unless a thread event like raise or kill tell
us to divert from the normal path of execution. The only possible
outcomes from interrupting a lock acquisition are to keep trying
until we have the lock or error out. This patch opts for the
former.

Fixes jruby#5875.

Previous logic used the same semaphore to sleep as any other sleep
which interfered with code that expected the Mutex to be the lock
used. The new logic uses the Mutex's JDK Lock, via a Condition, to
do the sleeping.

Because it is not possible for us to change the artificial thread
status we maintain to "sleep" after the lock is released, this
modified logic also introduces a new thread state that indicates
that the native JDK thread state should be used. This gets closer
to avoiding the racing status.

It does not appear to eliminate the race altogether.

Fixes jruby#5863.