Remove bypass method in ObserverContext and implement the 'bypass' logic case by case

Removes blanket bypass mechanism (Observer#bypass). Instead, a curated subset of methods are bypassable.     Changes Coprocessor ObserverContext 'bypass' semantic. We flip the     default so bypass is NOT supported on Observer invocations; only a     couple of preXXX methods in RegionObserver allow it: e.g. preGet     and prePut but not preFlush, etc. Everywhere else, we throw     a Exception if a Coprocessor Observer tries to invoke bypass. Master     Observers can no longer stop or change move, split, assign, create table, etc.     preBatchMutate can no longer be bypassed (bypass the finer-grained     prePut, preDelete, etc. instead)     Ditto on complete, the mechanism that allowed a Coprocessor     rule that all subsequent Coprocessors are skipped in an     invocation chain; now, complete is only available to     bypassable methods (and Coprocessors will get an exception if     they try to 'complete' when it is not allowed).     See javadoc for whether a Coprocessor Observer method supports     'bypass'. If no mention, 'bypass' is NOT supported. The below methods have been marked deprecated in hbase2. We would have liked to have removed them because they use IA.Private parameters but they are in use by CoreCoprocessors or are critical to downstreamers and we have no alternatives to provide currently. @Deprecated public boolean prePrepareTimeStampForDeleteVersion(final Mutation mutation, final Cell kv, final byte[] byteNow, final Get get) throws IOException {                @Deprecated public boolean preWALRestore(final RegionInfo info, final WALKey logKey, final WALEdit logEdit) throws IOException { @Deprecated public void postWALRestore(final RegionInfo info, final WALKey logKey, final WALEdit logEdit) throws IOException {         @Deprecated public DeleteTracker postInstantiateDeleteTracker(DeleteTracker result) throws IOException Metrics are updated now even if the Coprocessor does a bypass; e.g. The put count is updated even if a Coprocessor bypasses the core put operation (We do it this way so no need for Coprocessors to have access to our core metrics system).