Added INSERT and EXTRACT intructions from AVX-512 ISA.
All insertf*/extractf* functions replaced with insert/extract since we have insertf and inserti forms.
Added lowering for INSERT_VECTOR_ELT / EXTRACT_VECTOR_ELT for 512-bit vectors.
Added lowering for EXTRACT/INSERT subvector for 512-bit vectors.
Added a test.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@187491 91177308-0d34-0410-b5e6-96231b3b80d8