[InstSimplify] Remove redundant {insert,extract}_vector intrinsic chains

This commit removes some redundant {insert,extract}_vector intrinsic
chains by implementing the following patterns as instsimplifies:

   (insert_vector _, (extract_vector X, 0), 0) -> X
   (extract_vector (insert_vector _, X, 0), 0) -> X

Reviewed By: peterwaller-arm

Differential Revision: https://reviews.llvm.org/D101986