Update 404/500 to split out suggested actions for form builder and form filler

# Update 2
https://github.com/cds-snc/platform-forms-client/issues/401

## Description

Different CTAs that are appropriate to each audience when these pages 404/500 are encountered, whether from the app or from a public-facing form

**Problem:** End users filling out a form (form fillers) get a page that redirects them to Support.

## Context

Follow up to #4502 which covered generic errors for basic form elements.

## User story

As an end-user, I need more specific next steps when something goes wrong, so that I can navigate back to the right place or know what to do next.

## Additional detail

See rows: 17-22
https://docs.google.com/spreadsheets/d/1qx6K-PkburkQ2anDbRAhLpgWIfbYF8aWV6N34NrFUp8/edit?gid=0#gid=0

## Acceptance criteria

- [ ] Includes English and French error message content
- [ ] Right message is displayed to right audience (segmenting builders and fillers)
- [ ] Displays properly in Chrome, Firefox, Edge, Safari, and Opera
- [ ] Reads in the expected order on screen reader
- [ ] Works when there are multiple similar errors triggered on a page
- [ ] Provides context for the error focus state at the top of the error message list
- [ ] Links to the correct error / question
- [ ] Meets WCAG 2.1 AA requirements