Quote filenames in error messages

Quote filenames in error messages

The majority of all filenames are quoted in user facing error and
log messages, but a few were still printed without quotes.  While
these filenames do not risk causing any ambiguity as their format
is strict, quote them anyways to be consistent across all logs.

Also concatenate a message to keep it one line to make it easier
to grep for in the code.

Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://postgr.es/m/080EEABE-6645-4A46-AB20-6285ADAC44FE@yesql.se