Feature/rgb animation refactor

[Sapphirewhale]

Hi all! This is my first time contributing to this repo (also first time working on an OS, and first time writing C since uni), so feel free to let me know if you have any feedback on the code or PR. Here's the summary of my changes:

• Refactors the existing underglow effects system to make it easier to add new effects and effect callbacks
• Adds a new dts binding to provide board developers with a way to map LED positions to physical positions
• Adds a new underglow effect callback for key presses, with an accompanying listener
• Adds three new LED effects:
  • Matrix: Has leds light up in sequence following columns down the keyboard, with previous LEDs fading, simulating code monitors from the matrix
  • Glitter: Lights up leds corresponding to the pressed keys
  • Ripple: Lights up leds in an expanding circle around the pressed keys (this one has some performance issues :( )

Tested on a glove80 with both this repo and the version written from the moergo-sc fork.
I did write this all in the hopes that it would work out of the box on a different keyboard, but I don't have one available to test with, so if you're feeling up to writing up the underglow transform and testing it on your own board, feel free to let me know if you have any issues and I can try to fix it up.

The effects I've added are things that I figured would help break down my testing, and that I personally enjoyed, but I'm happy to break them out into a separate PR or remove them entirely, my main goal was to make this code easier to modify for anyone else in the community with fun ideas for LED effects.
The ripple effect was the main effect I wanted to implement, but I'm afraid that it's not especially performant, if you have the time and motivation to work out what's causing that and fix it I would greatly appreciate it.

I'm also happy to write up some basic documentation on how to add effects and use some of the utility functions if anyone could point me to a good spot in the docs.

PR check-list

• Branch has a clean commit history
• Additional tests are included, if changing behaviors/core code that is testable.
• Proper Copyright + License headers added to applicable files (Generally, we stick to "The ZMK Contributors" for copyrights to help avoid churn when files get edited)
• Pre-commit used to check formatting of files, commit messages, etc.
• Includes any necessary documentation changes.

[Nick-Munnich]

I'm afraid that this comment of mine also applies here.