cmd/asm: support Advanced Matrix Extensions (AMX) in Go Assembler

[henkjan-sneller]

The Go assembler (shipped with 1.20.5) currently lacks support for Advanced Matrix Extensions (AMX), particularly the sub-extensions AMX-TILE, AMX-INT8, and AMX-BF16.

As a workaround, we have been using byte sequences to generate the required instructions. However, for the sake of our mental stability, we would love to use proper instructions. @golang/compiler could you please add these 12 AMX instructions.

[ianlancetaylor]

This doesn't need to be a proposal, so taking it out of the proposal process.

[cagedmantis]

/cc @golang/compiler

[anton-kuklin]

Would love to work on that.

[cherrymui]

@anton-kuklin that would be great. Thanks! (I don't know of anybody currently working on this.)

[anton-kuklin]

Sure, starting my work.