Testing zero-copy bugs fixes (not for merging)

[szetszwo]

This fix will be split into multiple JIRAs: RATIS-2164, RATIS-2151, RATIS-2173

The following are the bugs found so far:

1. LeakDetector: asserted allLeaks is non-empty but printed "allLeaks.size = 0"
   • Another bug: Tracks are added to the set before calling retain. Without calling retain at all, it is not a leak.
2. SimpleTracing and AdvancedTracing: the methods should be synchronized.
   • Minor presentation problem: AdvancedTracing should have a single track list instead of retainsTraces and releaseTraces.
3. GrpcClientProtocolService.UnorderedRequestStreamObserver.processClientRequest(..) should use try-finally.
4. GrpcLogAppender.appendLog(..) calls release() incorrectly for exception.
5. LogAppenderDefault.sendAppendEntriesWithRetries(..) calls release() incorrectly for exception.
6. LogSegment cache can release an entry multiple times.
7. LogSegment.loadCache(..) should call retain() for cache hit.
8. SegmentedRaftLog.retainLog(..): between getting the entry and calling retain(), the entry can be released. The "fail to retain" exception, if there is any, can be ignored since It is the same as a cache miss. See #1153
9. SegmentedRaftLog.retainEntryWithData(..) should release for exception.
10. Test bug: the log entries stored in SimpleStateMachine4Testing can be released.
11. LogSegment: New entries can be added after EntryCache is closed.
12. MemoryRaftLog has similar problems as in SegmentedRaftLog.
13. SegmentedRaftLogWorker should clean up unfinished tasks in the queue after stopped running.