A major overhaul accounting for all music in 26.2

It was increasingly unfair how I made pools mutually exclusive because the pool of music being exclusive to mountain biomes was increasing rapidly, and themed songs like the desert songs needed addressing, and

I've basically made many pools of 2-5 songs and each pool has slightly different weights in every sound event. The weights range from 2 to 5, so every song still has a reasonable of playing in every biome.

The songs should get overall equal treatment, there's nothing like the Chaos Cubed soundtrack in vanilla getting double the weight.

A smaller change is that I've moved komorebi from underwater to the overworld, and O's Piano from the overworld to underwater. I added the 2026 songs, and Ebb is the only one that will play in the menu, the rest are in overworld pools.

Finally, I've updated the volume of many newer songs to try and keep it consistent. This was inspired by Minecraft: Askew, but I did my own testing and chose the values myself.

Thanks for sticking around! I'm still not sure how biome-dependent to make stuff while keeping it fair, so I'd love for you to try it out and give feedback! The PMC forum is in the links. =]