[X86] Add avx512 scatter intrinsics that use a vXi1 mask instead of a scalar integer.

[X86] Add avx512 scatter intrinsics that use a vXi1 mask instead of a scalar integer.

We're trying to have the vXi1 types in IR as much as possible. This prevents the need for bitcasts when the producer of the mask was already a vXi1 value like an icmp. The bitcasts can be subject to code motion and interfere with basic block at a time isel in bad ways.

llvm-svn: 351275