[FIX] survey: support custom server date format in (frontend) surveys

The library moment.js does not support custom date formats anymore.
The following warning is given:
Deprecation warning: value provided is not in a recognized ISO format.
As a result, the moment contains 'Invalid Date',
which would remove possibility to complete a survey containing a date
in any format different than the default.

opw 1930152

closes odoo/odoo#30894