[GlobalISel] add additional lowering support for G_INSERT

Summary: Add lowering support for inserting pointers or scalars into scalars, vectors or pointers

Reviewers: arsenm, dsanders

Reviewed By: arsenm

Subscribers: jvesely, wdng, nhaehnle, rovka, hiraditya, volkan, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75994