[BUGFIX] TypeConverter can handle oldschool classnames

In case an extension provides oldschool classnames, the
setTypeConverterOptions functions fail due to mismatched arraykey.
This key is the classname of the converter.
Test for oldschool classnames and replace the arraykey with the
namespaced version solves the issue.

Fixes: #45977
Releases: 6.0, 6.1
Change-Id: I88debadda628ee166aea6ebdbf173a6239779303
Reviewed-on: https://review.typo3.org/18709
Reviewed-by: Stefan Neufeind
Tested-by: Stefan Neufeind
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters