[X86] Move more isel patterns to X86InstrVecCompiler.td. NFC

This moves more of our subvector insert/extract tricks to X86InstrVecCompiler.td and refactors them into multiclasses.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@312661 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed