Distinct names for end user html form files saved "in progress" vs. "once submitted"

## Description
When going through the flow for "save and resume", I kept being asked if I wanted to overwrite the file I'd already saved.

ex: `form-title-formID.html`

We might consider a different naming convention for files while in progress versus once submitted to help users differentiate and keep the right ones at a glance.

## Steps to reproduce
1. Go to a published form with the "Save answers" setting ON
2. Fill in some fields and "Save to device"
3. Close the tab and reupload your answers
4. Continue through to review page and submit
5. Download a copy of answers submitted
6. See the prompt to overwrite the file

## Details
- **Browser**: Chrome
- **Operating system**: Mac
- **Environment**: Production
- **Language**: English/French
- **Viewport**: Desktop
- **Output**: https://forms-formulaires.alpha.canada.ca/en/id/cm98mduls000yyd01jwibk2bn

## Expected behaviour
Different status leading to different form file naming convention?

## Screenshots or videos

Start by tracing the save-and-resume and submitted-answer download flows described in the reproduction steps, focusing on where the HTML filename is selected. Reproduce the overwrite prompt in the linked production form, then verify that in-progress and submitted files receive distinct names without prompting to overwrite the other status.

Written by the indexing model from the issue text.