Prompt users that contact information should accompany File upload form element

# File upload v2

## Context

Based on next iteration of #5619

For Beta cohort, this is encouraged and nudged but not blocked. (Add contact information to be able to follow up)

`Adding a “file upload” element to 
your form requires the collection 
of contact information.`

When we release file attachments more widely we'll want to consider having these be stronger warnings, or requirements,, or companion components, or for users to have a path to recover if their files are corrupted or flagged as malicious, making their form or application incomplete.

## Goal

**Implement a process to ensure that forms with file upload components also collect contact information** _Recommended by Policy_

## Additional context

**Action item from:** File scanning service journey (2022) https://docs.google.com/document/d/124-Se6WiZVzpXQ-0JkHQZYVyc4RZa0JDI1iwaB-UG6E/edit?tab=t.0#heading=h.2xcijnehx2zv

Requiring that **all forms with file uploads also collect end-user contact information** in another format will help GC Forms ensure that clients can get in touch with end-users if they think the submission is legitimate.

Start by tracing the File upload v2 form-element flow and review the next iteration of #5619, then consult the File scanning service journey linked in the issue. Done means forms containing file uploads prompt for contact information, while the Beta cohort receives an encouragement rather than a block.

Written by the indexing model from the issue text.