Vulkan: MMVQ Integer Dot K-Quant and MUL_MAT_ID support (llama/16900)

Vulkan: MMVQ Integer Dot K-Quant and MUL_MAT_ID support (llama/16900)

* vulkan: split mul_mmq_funcs for mul_mat_vecq use

* add mxfp4 mmvq

* add q2_k mmvq

* add q3_k mmvq

* add q4_k and q5_k mmvq

* add q6_k mmvq

* handle 4x4 quants per mmvq thread

* enable MUL_MAT_ID mmvq support

* enable subgroup optimizations for mul_mat_vec_id shaders

* device tuning

* request prealloc_y sync after quantization

* fix indentation

* fix llvmpipe test failures

* fix mul_mat_id mmvq condition

* fix unused variable warning