[TASK] EXT:form - change naming and icon in new content element wizard

Change language labels and move them to ext:form locallang.xlf.
Change the icon to content-form.

Resolves: #81650
Releases: master, 8.7
Change-Id: I1c497b78da92dc589ad9d7a47dde35c5aeba488a
Reviewed-on: https://review.typo3.org/53957


Reviewed-by: Mathias Brodala <mbrodala@pagemachine.de>
Tested-by: Mathias Brodala <mbrodala@pagemachine.de>
Reviewed-by: Daniel Lorenz <daniel.lorenz@extco.de>
Tested-by: Daniel Lorenz <daniel.lorenz@extco.de>
Reviewed-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Tested-by: Bjoern Jacob <bjoern.jacob@tritum.de>
Reviewed-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Tested-by: Ralf Zimmermann <ralf.zimmermann@tritum.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Reviewed-by: Susanne Moog <susanne.moog@typo3.org>
Tested-by: Susanne Moog <susanne.moog@typo3.org>