Make IQ1_M work for QK_K = 64 (#6327)
* iq1_m: make it work for QK_K = 64 (WIP)
* iq1_m: make it work for QK_K = 64 (scalar and AVX2)
* iq1_m: QK_K = 64 seems to work on Metal and ARM_NEON
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Co-authored-by: Iwan Kawrakow <iwan.kawrakow@gmail.com>
