We sometimes see a `ShardLockObtainFailedException` when a shard failed
to shut down as fast as we expected, often because a node left and
rejoined the cluster. Sometimes this is because it was held open by
ongoing scrolls or PITs, but other times it may be because the shutdown
process itself is too slow. With this commit we add the ability to
capture and log a thread dump at the time of the failure to give us more
information about where the shutdown process might be running slowly.
Relates #93226
4c68382065