[FIX] survey: display right date format in datepicker

Issue

	- Install 'Survey' & 'website' module
	- Enable "es_VE" language and activate on main website
	- Go to Website Homepage
	- Switch to "Spanish (VE)" language (footer)
	- Go to "Survey" module
	- Create a survey:
	- Add a question of type 'Date' then save
	- Click on "TEST" button
	- Start survey and add a date with the datepicker
	- Submit survey

	Error message : 'This is not a date'

Cause

	When submit survey, not using the database date format.

Solution

	When validating form (on submit), check if date is formated
	with database format and (not the moment locale since user can
	alter date and datetime format).

opw-2452237

closes odoo/odoo#70273

X-original-commit: ddfcecc6
Signed-off-by: Anh Thao PHAM <kitan191@users.noreply.github.com>