avx512: add _mm512_{,mask_,mask2_,maskz_}permutex2var_epi{8,16} intrinsics

Add _mm512_{,mask_,mask2_,maskz_}permutex2var_epi{8,16} intrinsics to permutex2var.[ch]

Add NEON translations for _mm512_permutex2var_epi{8,16,32}
This could easily be done for _mm512_permutex2var_epi64 too.
However it may not be faster than the portable version.
There are decreasing returns as the size increases.