IGNITE-29108 Add explicit lock hold time metrics

[NSAmelchev]

There was no way to see how long explicit locks acquired with IgniteCache.lock() are held: a leaked lock blocks other threads and the partition map exchange, but it is neither a transaction nor a future, so neither the metrics nor the long running operations dump showed it.

Two metrics are added to the tx registry, collected on the node that acquired the lock:

• MaxExplicitLockHoldTime — maximum hold time of the explicit locks currently held, in milliseconds.
• ExplicitLockHoldTimeHistogram — hold times of released explicit locks, one sample per lock()/lockAll() call.

The "Pending explicit locks" dump of a stuck PME now shows the hold time of every key.