UI: Add prefix and suffix for remux

[NikitaCartes]

Description

Added ability to save remuxed files with suffixes and prefixes, similar to Replay Buffer.

Motivation and Context

This will make it easier to sort and search remuxed files. Prefix will allow saving files in a separate folder (as it done in Replay Buffer Prefix). This was a regular request on the OBS forum: one, two, three

How Has This Been Tested?

Added/removed settings while watching remux files being saved.

Types of changes

New feature (non-breaking change which adds functionality)

Checklist:

• [x] My code has been run through clang-format.
• [x] I have read the contributing document.
• [x] My code is not on the master branch.
• [x] The code has been tested.
• [x] All commit messages are properly formatted and commits squashed where appropriate.
• [x] I have included updates to all appropriate documentation.

[NikitaCartes]

Re-tested again after rebasing onto master