[X86, AVX2] Replace inserti128 and extracti128 intrinsics with generic shuffles

[X86, AVX2] Replace inserti128 and extracti128 intrinsics with generic shuffles

This is nearly identical to the v*f128_si256 parts of r231792 and r232052.

AVX2 introduced proper integer variants of the hacked integer insert/extract
C intrinsics that were created for this same functionality with AVX1.

This should complete the front end fixes for insert/extract128 intrinsics.
Corresponding LLVM patch to follow.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@232109 91177308-0d34-0410-b5e6-96231b3b80d8