Much faster prompt processing for IQK quants (ARM_NEON) (#549)

* Faster GEMM fir iq2_ks, iq4_ks

* iq5_ks

63.8 t/s -> 166 t/s. iq5_ks_r4 is at 107.4 t/s.
But: iw5_ks_r4 TG performance is quite a bit better:
21.7 t/s vs 17.7 t/s for iq5_ks.

* iq6_k

44 t/s -> 164.3 t/s. There is no iq6_k_r4

* iq5_k

46 t/s -> 167 t/s. iq5_k_r4 is at 99.5 t/s.

* iq4_k

46.4 -> 167.2 t/s. iq4_k_r4 is at 115 t/s.

* iq3_k

47.3 t/s -> 166.5 t/s. iq3_k_r4 is at 96.5 t/s.

* iq2_k

47.4 t/s -> 167 t/s. iq2_k_r4 is at 113.3 t/s.

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Co-authored-by: Iwan Kawrakow <[email protected]>

Author: ikawrakow