[BUGFIX] Fix functional tests for EXT:frontend on PostgreSQL

Replace the MySQL specific backtick quoting with the actual quote
character in test checking for SQL fragments/quoting of fields.

Change assertions that assume integer return values from the
database driver to also accept string types using assertEquals().

Resolves: #79797
Releases: master
Change-Id: I1f78b0b65cdcceeaefa23902d14fa0988198d849
Reviewed-on: https://review.typo3.org/51764


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Manuel Selbach <manuel_selbach@yahoo.de>
Reviewed-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Tested-by: Mona Muzaffar <mona.muzaffar@gmx.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>