[TASK] Functional test for VariableFrontend cache type

[TASK] Functional test for VariableFrontend cache type

Add a functional test to verify that serialized PHP objects
can be successfully stored in the database without having
encoding/escaping problems.

Resolves: #79452
Releases: master
Change-Id: I97d586cb8a50e571d99ff8b7fc463c0a83e15f36
Reviewed-on: https://review.typo3.org/51394
Reviewed-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: Morton Jonuschat <m.jonuschat@mojocode.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Manuel Selbach <manuel_selbach@yahoo.de>
Tested-by: Manuel Selbach <manuel_selbach@yahoo.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>