Add temporary debug info to help debug 019_replslot_limit.pl failures.
I have not been able to reproduce the occasional failures of
019_replslot_limit.pl we are seeing in the buildfarm and not for lack of
trying. The additional logging and increased log level will hopefully help.
Will be reverted once the cause is identified.
Discussion: https://postgr.es/m/
20220218231415.c4plkp4i3reqcwip@alap3.anarazel.de