Add preferences to configure replay gain

Description

This MR adds configuration parameters to support replay gain functionality which already exists within libVLC.

How Has This Been Tested?

1. Audio playback works as expected
2. Config parameters confirmed to adjust audio levels

Known Issues

1. Video playback does not seem to use the replay gain settings
2. Modifying replay gain settings during video playback triggers the last-played audio file to start playing
3. The TV UI does not limit the keyboard input characters in the same manner as the phone UI keyboard (May require additional input validation)

Types of changes

• New feature (non-breaking change which adds functionality)

Checklist

• I have read the CONTRIBUTING section of the README document.

Resolves

Fixes: #1912 (closed)