[WebAssembly] Move/clone DBG_VALUE during WebAssemblyRegStackify pass

Summary:
The MoveForSingleUse or MoveAndTeeForMultiUse functions move wasm instructions,
however DBG_VALUE stay unchanged -- moving or cloning these.

Reviewers: dschuff

Reviewed By: dschuff

Subscribers: mattd, MatzeB, dschuff, sbc100, jgravelle-google, aheejin, sunfish, llvm-commits, aardappel

Tags: #debug-info

Differential Revision: https://reviews.llvm.org/D49034

llvm-svn: 343007