[BUGFIX] Fix and clean up EXT:belog module

Fixes
=====

* Fix DateTimePicker by adding the correct format
  as required since updating to flatpickr in #91606
* Restore clearable functionality of DateTime fields
  by adding a new TypeScript Module, which properly
  initializes those fields.
* Unify size of form fields again and fix position
  of the submit button and the `groupByPage` checkbox
* Add bootstrap v5 compatible markup to the `groupByPage`
  checkbox

Cleanup
=======

* Unify UX by using the `actions-calendar` icons,
  like FormEngine does, instead of font awesome.
* Add type annotations and return types, where possible
* Avoid usage of ObjectManager->get()

Resolves: #94020
Releases: master
Change-Id: I5ae684871c7ba5003d6c873604a2ca81067f7f27
Reviewed-on: https://review.typo3.org/c/Packages/TYPO3.CMS/+/68912


Tested-by: core-ci <typo3@b13.com>
Tested-by: Benni Mack <benni@typo3.org>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Benni Mack <benni@typo3.org>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>