NoneOf and AnyOf can validate multiple valued fields

[azmeuk]

Fixes NoneOf/AnyOf validators not managing SelectMultipleField data.

>>> import wtforms
... from werkzeug.datastructures import ImmutableMultiDict
... class F(wtforms.Form):
...     foo = wtforms.SelectMultipleField(
...         choices=["bar", "baz"],
...         validators=[wtforms.validators.none_of(["baz"])],
...     )
>>> F(ImmutableMultiDict({"foo": "bar"})).validate()
True
>>> F(ImmutableMultiDict({"foo": "baz"})).validate()
True

Replaces #538
Related to #799