suppressing useless wakeups in logical/worker.c

Hi hackers,

I've attached an attempt at porting a similar change to 05a7be9 [0] to
logical/worker.c.  The bulk of the patch is lifted from the walreceiver
patch, but I did need to add a hack for waking up after
wal_retrieve_retry_interval to start sync workers.  This hack involves a
new wakeup variable that process_syncing_tables_for_apply() sets.

For best results, this patch should be applied on top of [1], which is an
attempt at fixing all the stuff that only runs within a reasonable
timeframe because logical worker processes currently wake up at least once
a second.  With the attached patch applied, those periodic wakeups are
gone, so we need to make sure we wake up the logical workers as needed.

[0] https://postgr.es/m/CA%2BhUKGJGhX4r2LPUE3Oy9BX71Eum6PBcS8L3sJpScR9oKaTVaA%40mail.gmail.com
[1] https://postgr.es/m/20221122004119.GA132961%40nathanxps13

-- 
Nathan Bossart
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