[TASK] DatabaseSessionBackend: Pass on DB exception information

We add the original message from the DBAL exception to our custom
message in the session backend exception.

Resolves: #79781
Releases: master
Change-Id: I8aec6ba5dcee097f65d4f06916e158092fa31f04
Reviewed-on: https://review.typo3.org/51657


Reviewed-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: Mathias Schreiber <mathias.schreiber@typo3.com>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>