[!!!][FEATURE] EXT:form - add content element uid to the form identifier

Make it possible to use the same form multiple times on one page by
adding the content element uid to the form identifier.

Resolves: #81775
Releases: master
Change-Id: I001a654f8ffc47c91c984133d8475605f1b15b7a
Reviewed-on: https://review.typo3.org/54125
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Joerg Boesche <typo3@joergboesche.de>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>
Reviewed-by: Georg Ringer <georg.ringer@gmail.com>
Tested-by: Georg Ringer <georg.ringer@gmail.com>