MVCC management and monitoring

This is an umbrella ticket for MVCC management and monitoring capabilities. This should include (but not limited to):

1. Proper cache metrics (standard cache operations, number of stale versions aka "bloat", etc)
2. MVCC coordinator metrics (node ID, number of received requests, number of active TXes, current cleanup version, current version, etc)
3. Cache events (either standard JCache or something else)
4. Deadlock detector metrics
5. Vacuum performance/metrics
6. TxLog metrics