Make motion submission date editable

[Elblinator]

needs OpenSlides/openslides-backend#2112

Current behaviour:
currently the submission date is automatically created by the program

Wanted behaviour:

• This submission date should be editable by participants with the permission motion.can_manage_meta_data.
• The submission date needs the edit icon next to the string
• if the submission date is being edited a date and time picker needs to open.

[reiterl]

The backend issue needs to be resolved first.

[jsangmeister]

Backend PR exists: OpenSlides/openslides-backend#2194