[X86][AVX] Fold concat(ps*lq(x,32),ps*lq(y,32)) -> shuffle(concat(x,y),zero) (PR46621)

[X86][AVX] Fold concat(ps*lq(x,32),ps*lq(y,32)) -> shuffle(concat(x,y),zero) (PR46621)

On AVX1 targets we can handle v4i64 logical shifts by 32 bits as a pair of v8f32 shuffles with zero.

I was hoping to put this in LowerScalarImmediateShift, but performing that early causes regressions where other instructions were respliting the subvectors.