[X86][Costmodel] Load/store i16 VF=2 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/M8vEKs5jY - for intels `Block RThroughput: =2.0`;
                                  for ryzens, `Block RThroughput: <=1.0`
So pick cost of `2`.

For store we have:
https://godbolt.org/z/Kx1nKz7je - for intels `Block RThroughput: =1.0`;
                                  for ryzens, `Block RThroughput: <=0.5`
So pick cost of `1`.

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/D103144