[FIX] survey: fix date picker template and validation

The date picker widget was set to text instead of date.
Then we needed to fix the date validation at form submit.

opw 1890130

closes odoo/odoo#27448

addons/survey/static/src/js/survey.js

@@ -134,7 +134,7 @@ if(!the_form.length) {
             var date_fields = $form.find('div.date > input.form-control');
             for (var i=0; i < date_fields.length; i++) {
                 var el = date_fields[i];
-                var moment_date = $(el).data('DateTimePicker').date();
+                var moment_date = moment(el.value);
                 if (moment_date) {
                     moment_date.toJSON = function () {
                         return this.clone().locale('en').format('YYYY-MM-DD');

addons/survey/views/survey_templates.xml

@@ -238,7 +238,7 @@
 
     <template id="date" name="Date box">
         <div class='input-group date'>
-            <input type="text" date="true" class="form-control date" t-att-name="prefix"/>
+            <input type="date" class="form-control" t-att-name="prefix"/>
         </div>
     </template>