Summary:
 Api to allow releasing locks for a session/host when either
 a) The session ends, or
 b) The tserver loses its lease/restarts.

 The TServer should detect when a session ends, and may call
 the API to release all locks held by a particular session.

 Once YSQL lease is implemented, the master may realize that
 a TServer has lost it's lease, or
 may discover that the TServer has had a restart when a TServer
 shows up with a new instance_seqno. A new incarnation-id may
 be generated, and then a background task clears out the locks
 held by previous incarnations.

 Other changes:
 - Try to make Unlock/Lock apis take a callback instead
Jira: DB-13773

Test Plan: yb_build.sh --cxx-test object_lock-test

Reviewers: zdrudi, bkolagani

Reviewed By: zdrudi

Subscribers: ybase

Differential Revision: https://phorge.dev.yugabyte.com/D39749