Support AlphaFold2

[martin-steinegger]

AlphaFold2 is heavily used by the life science community to predict protein structures. AlphaFold is written in Jax and already runs on CPUs. However, it would be amazing to have a CPU version with ggml with all the speed-ups achieved through quantization.

Deepmind has recently implemented bfloat16 inference with pretty much equivalent performance. I think further quantization should be possible and beneficial.

Additionally, having a (python) dependency-free implementation would help us a lot in ColabFold.