Better required field handling in Request Study

[candu]

Description
In Request Study, the user currently has to interact with a field and "dirty" it before it can trigger the invalid state, which then highlights those fields.

This combined with disabling the Submit button until the form is completed leads to a UX Catch-22: they have to fill out the required fields, but they don't know which ones those are until they fill them out!

Acceptance Criteria

• validation on due date, additional CCs, and urgent reason fields triggers as soon as the request is marked urgent, rather than on dirty;
• due date is still only shown for urgent requests;
• clicking the calendar icon on due date opens the calendar;
• when the request is marked urgent, and when a required field is successfully filled out, that field is displayed in a success state.