Add hacky via support for RGB Matrix

[drashna]

Description

Adds rgb matrix functions for via's lighting system, rather than the hacky rgblight stuff.

This only adds support on qmk side, as via is developed independently of qmk.

Types of Changes

• Core
• Enhancement/optimization

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).