[X86][Costmodel] Load/store i16 Stride=2 VF=32 interleaving costs

The only sched models that for cpu's that support avx2
but not avx512 are: haswell, broadwell, skylake, zen1-3

For load we have:
https://godbolt.org/z/q6GbK89br - for intels `Block RThroughput: =18.0`; for ryzens, `Block RThroughput: <=7.0`
So pick cost of `18`.

For store we have:
https://godbolt.org/z/Yzfoo5TnW - for intels `Block RThroughput: =8.0`; for ryzens, `Block RThroughput: <=4.0`
So pick cost of `8`.

I'm directly using the shuffling asm the llc produced,
without any manual fixups that may be needed
to ensure sequential execution.

Reviewed By: RKSimon

Differential Revision: https://reviews.llvm.org/D110507