Reduce idle FATE worker polling interval

[DomGarguilo]

Related to #5827

On a 5 node test cluster I hit the cost of this issue testing 4.0.0-alpha. The cluster was idle with no fate transactions and the fate workers were still burning 24% of a core on one manager and 72% on another. ~26 workers all waking up 1000 times a second on an empty queue. Measured from thread dumps 60s apart.

#5825 replaced the poll(100, MILLISECONDS) with poll() + Thread.sleep(1) so 100x the wakeups. Sleeping for 50 or 100ms would get most of that back now without waiting for JDK 21. Working on a PR for that now.

Originally posted by @DomGarguilo in #5827

This PR increases the sleep interval to 50ms to vastly decrease this idle usage described above. The new interval is derived from the tryTransfer timeout (100ms) so that it is still guaranteed the worker will poll at least once while the work finder is waiting to hand off.