[ScalarizeMaskedMemIntrin] Use IRBuilder functions that take uint32_t/uint64_t...

[ScalarizeMaskedMemIntrin] Use IRBuilder functions that take uint32_t/uint64_t for getelementptr, extractelement, and insertelement.

This saves needing to call getInt32 ourselves. Making the code a little shorter.

The test changes are because insert/extract use getInt64 internally. Shouldn't be a functional issue.

This cleanup because I plan to write similar code for expandload/compressstore.

llvm-svn: 355767