966 use bevy meshes as nannous rendering backend

[tychedelia]

Another messy diff. But, overall, this works!

Notes:

• Right now, we are taking the most naive approach for caching meshes, which is just to query and iterate through existing meshes and spawn new ones as needed.
• A lot of the churn is from switching to use Bevy's color in our public API. Note that this is changing in bevy 0.14, with the addition of lots of new color spaces we'll want to support. https://github.com/bevyengine/bevy/issues/10986 There's probably more cleanup work we could do here to make things nice.
• I haven't ripped out the text rendering backend yet, but we'll want to track and switch to this https://github.com/bevyengine/bevy/issues/7616.

TODO:

• [ ] Check all primitives still render.