vulkan: support SET_ROWS (llama/14587)

vulkan: support SET_ROWS (llama/14587)

* vulkan: support SET_ROWS

Add variants of the copy_to_quant shader that do the SET_ROWS operation.
Change these shaders to spread the work across the workgroup.
The memory access pattern is probably not great (one thread per quant block),
but should be fine for now.

* vulkan: optimize set_rows

Larger workgroups for non-quant types.
Set "norepeat" (there is manual repeat logic).
Use fastmod.