Use hba_file/ident_file GUCs rather than pg_hba.conf/pg_ident.conf in logs

Use hba_file/ident_file GUCs rather than pg_hba.conf/pg_ident.conf in logs

This is particularly useful when log_min_messages is set to FATAL, so as
one can know which file was not getting loaded whether hba_file or
ident_file are set to some non-default values.  If using the default
values of these GUC parameters, the same reports are generated.

This commit changes the load (startup) and reload (SIGHUP) messages.

Author: Julien Rouhaud
Discussion: https://postgr.es/m/20220223045959.35ipdsvbxcstrhya@jrouhaud