[TASK] EXT:form - rename form element "Page" to "Step"

Resolves: #80194
Releases: master, 8.7
Change-Id: I6b08f5f9593c83dc8b28c1d16fab4ae2517a139a
Reviewed-on: https://review.typo3.org/53405


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Andreas Fernandez <typo3@scripting-base.de>
Tested-by: Andreas Fernandez <typo3@scripting-base.de>
Reviewed-by: Henrik Elsner <helsner@dfau.de>
Tested-by: Henrik Elsner <helsner@dfau.de>
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>