Use Design System date format in Support app

[AgaDufrat]

What

Replace date picker in the following forms:

• “Request a new campaign”
• “Remove user”
• “Content change request”
• “Content advice and help”
• Feedback Explorer "Total quantity by day" (https://support.publishing.service.gov.uk/anonymous_feedback/explore)

in Support app to use Design System date format: https://design-system.service.gov.uk/patterns/dates/ (separate fields for day, month, year). Add relevant validations.

NB: we are not converting the forms to Design System

• Remove "jquery-ui-rails" dependency https://github.com/alphagov/support/blob/main/Gemfile#L18 and any related JS.

• Reply to the Zendesk ticket.

Why

Date picker arrows in Support app stopped working after the migration to Dart Sass. It’s caused by a known issue in the way Dart Sass handles the icon as Unicode - sass/sass#1395 we were not able to find a workaround. Date picker are not very accessible. When users are filling the dates in the form they normally know them already (and don’t need to pick it by looking at a calendar).

Users see a  symbol instead of an arrow. There’s alt text (Next, Prev). It’s also possible to enter date manually.

This will allow us to drop dependency on jquery-ui-rails.

[nicholsj]

Reopening because we still need to remove date picker from 2 fields in Feedback Explorer: https://support.staging.publishing.service.gov.uk/anonymous_feedback/explore
before we can remove "jquery-ui-rails" dependency.

I've added that to the task list