Introduce lowbit quantized linear MPS kernels #3757

Job	Run time
test (CPU Nightly, linux.4xlarge, --pre torch --index-url https://download.pytorch.org/whl/nightl... / linux-job	7m 19s
test (CPU 2.4, linux.4xlarge, torch==2.4.0 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job	7m 55s
test (CPU 2.3, linux.4xlarge, torch==2.3.0 --index-url https://download.pytorch.org/whl/cpu, cpu) / linux-job	6m 1s
test (CPU 2.2.2, linux.4xlarge, torch==2.2.2 --index-url https://download.pytorch.org/whl/cpu "nu... / linux-job	4m 15s
test (CUDA 2.2.2, linux.g5.12xlarge.nvidia.gpu, torch==2.2.2 "numpy<2" , cuda, 12.1) / linux-job	15m 45s
test (CUDA 2.3, linux.g5.12xlarge.nvidia.gpu, torch==2.3.0, cuda, 12.1) / linux-job	23m 34s
test (CUDA 2.4, linux.g5.12xlarge.nvidia.gpu, torch==2.4.0, cuda, 12.1) / linux-job	32m 26s
test (CUDA Nightly, linux.g5.12xlarge.nvidia.gpu, --pre torch --index-url https://download.pytorc... / linux-job	46m 39s
	2h 23m 54s

Provide feedback