[CLEANUP] Code cleanup in ModuleMenu.js

Adds some JS doc and renames few properties to make code more readable.

Resolves: #82775
Releases: master
Change-Id: I8cb66ee1d52be00ea6e556d369607aecc7e4e2fb
Reviewed-on: https://review.typo3.org/54406


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>
Reviewed-by: Sebastian Fischer <typo3@evoweb.de>
Reviewed-by: Benni Mack <benni@typo3.org>
Tested-by: Benni Mack <benni@typo3.org>