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

Detect errors during execution of SQL statements using the
exceptions thrown by Doctrine DBAL instead of trying to use
Connection::errorCode().

The previous code doesn't work on MySQL if an actual error
occurs since an exception would be thrown earlier in the
process and the relevant code path would not be reached.

The happy path worked before because MySQL returns 0 as the
code when a statement executed successfully while PostgreSQL
returns '00000' which PHP does not consider to be empty.

Resolves: #79801
Releases: master
Change-Id: I508966b6731d256d1edff2267669d158a8d647bf
Reviewed-on: https://review.typo3.org/51731


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>