[BUGFIX] No duplicate insertion in addToAllTCAtypes

This patch improves the regular expression in
ExtensionManagementUtility::executePositionedStringInsertion().

It is made sure that the field name ends with a comma or a line
ending to prevent duplicate insertions of the string when field
names start with the same substring.

Resolves: #55932
Releases: 6.2
Change-Id: I375c40760a38b7f939086bb851911bd7f52509ca
Reviewed-on: https://review.typo3.org/27583
Reviewed-by: Michiel Roos
Tested-by: Michiel Roos
Reviewed-by: Markus Klein
Tested-by: Markus Klein