Invalidate pgoutput's replication-decisions cache upon schema rename.

Invalidate pgoutput's replication-decisions cache upon schema rename.

A schema rename should cause reporting the new qualified names of
tables to logical replication subscribers, but that wasn't happening.
Flush the RelationSyncCache to make it happen.

(If you ask me, the new test case shows that the behavior in this area
is still pretty dubious, but apparently it's operating as designed.)

Vignesh C

Discussion: https://postgr.es/m/CALDaNm32vLRv5KdrDFeVC-CU+4Wg1daA55hMqOxDGJBzvd76-w@mail.gmail.com