ggml-cpu: aarm64: q6_K repack gemm and gemv (and generic) implementations (i8mm)...

ggml-cpu: aarm64: q6_K repack gemm and gemv (and generic) implementations (i8mm) #18860 (#18888)

* Boilerplate for q6_K repack

* q6_K repack to q6_Kx8 implementation

Signed-off-by: Alberto Cabrera <redacted>
* q6_K generic gemv and gemm

* wip, gemm_q6_K 8x8

* Still WIP: loading of q8s, q6h and q6l

* first working version of q6_K gemm

* Moved q6 loads outside of sb block, Unrolled inner loop

* Replaced modulo with mask

* First implementation of GEMV

* ggml_vdotq_s32 -> vdotq_s32

* Reduce width of accumulators in q6_K gemv

* Bsums instead of calc bias. Preload scales to use vget_lane. Unroll.

* Reuse scales in GEMM (same GEMV opt)

* Added todos for bsum and different qh repack

* Arch fallback

* VSLIQ for merging qh adn ql

* Removed TODO, already tested

* Apply suggestions

Co-authored-by: Georgi Gerganov <redacted>
* Removed unused import

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Signed-off-by: Alberto Cabrera <redacted>
Co-authored-by: Georgi Gerganov <redacted>