metal : add quantized FA support (#10149)

* metal : add quantized FA (vec) support

ggml-ci

* metal : add quantized FA (non-vec) support

* metal : fix support check

ggml-ci

* metal : clean-up

* metal : clean-up (cont)

* metal : fix shared memory calc + reduce smem + comments

* metal : float-correctness

* metal : minor [no ci]

Author: ggerganov