Explore expanding dynamic quantization kernels (broaden a8w4dq support)

[mikekgfb]

Add support for
1 - asymmetric a8w4dq, basically require to subtract zero from each value before multiplying, so should add a single multiply.
This will help accelerate and better handle GGUF files on executorch and read Q4_0 for export to mobile.
2 - a8w4dq on desktop
3 - the asymmetric version of (1) on desktop

[digantdesai]

Is this a new non-xnnpack route?