[TASK] Return __toString value from objects in DataMapper::getPlainValue

See if a object is a instance of \Stringable aswell as a TypeInterface.

TypeInterface implements the __toString method but objects coming
from extension can rely on either implements \Stringable or
have the __toString method

Resolves: #102263
Releases: main, 12.4
Change-Id: I840492b0011b60abc3754f215695154c90b7e707
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/81579


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: core-ci <typo3@b13.com>