[X86][AVX512] lower1BitShuffle - fold broadcast(setcc(x,y)) ->...

[X86][AVX512] lower1BitShuffle - fold broadcast(setcc(x,y)) -> setcc(broadcast(x),broadcast(y)) (PR52500)

AVX512 has excellent broadcast ops for everything but vXi1 bool vectors - so if we're broadcasting a comparison result, see if we can broadcast the comparison operands instead.