[REF] survey: refactor invitation wizard

Purpose is to clean and simplify invite wizard on surveys. Main purpose is
to simplify options.

Public link is displayed for public surveys, allowing to quickly share
it. When sending emails a token is now generated for each recipient. There is
no "batch public link" sending option anymore as it is not really necessary.

Check is done on recipients and emails to match the access mode option. Having
a restricted survey gives the same limitations on people to invite (users,
employees, ...).

Code is cleaned to ease its understanding and prepare future evolution notably
with appraisals.

An existing mode field is added on invite model. All options are currently
not used but it prepares future addition to survey, notably for certifications.
Its purpose is to know what to do with existing tokens when inviting new
recipients. It is used notably to resend tokens through the user_input form
view instead of relying on a custom context key.

This commit is linked to task ID 1911586 and PR #28986.