ggml-webgpu: updated matrix-vector multiplication (#21738)

* merged properly, but slow q3_k and q5_k with u32 indexing

* Start on new mat-vec

* New format float paths working

* Working q4_0

* Work on remaining legacy q-types

* port k-quants to new matvec

* remove old shader

* Remove old constants, format

* remove accidental file

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Co-authored-by: Neha Abbas <nehaabbas@ReeseLevines-MacBook-Pro.local>
Co-authored-by: Reese Levine <reeselevine1@gmail.com>