STASHDEV-7788 Remove the code to timeout remote operations on the remote node

STASHDEV-7788 Remove the code to send CallTimeoutException responses
from remote operation threads back to the caller to indicate timeout.
These are expensive to deserialize (especially when the contents of
the CallTimeoutException are not used for anything anyway), and when
the queue is long can lead to an indefinitely growing queue of retried
invocations.
I've just committed a change to WARN if an operation is ever processed that would have been aborted with `CallTimeoutException` under the old logic, plus record more statistics about the latency of operations from remote nodes to this point in the code.  This should inform us whether the decisions taken here are moving us in the right direction or not.