The PR removes calls to applierV3base logic from server.go that is NOT part of 'application'.
The original idea was that read-only transaction and Range call shared logic with Apply,
so they can call appliers directly (but bypassing all 'corrupt', 'quota' and 'auth' wrappers).
This PR moves all the logic to a separate file (that later can become package on its own).
When etcdserver receives a LeaseRenew request, it may be still in
progress of processing the LeaseGrantRequest on exact the same
leaseID. Accordingly it may return a TTL=0 to client due to the
leaseID not found error. So the leader should wait for the appliedID
to be available before processing client requests.
