[WebAssembly] Add debug info to insts in Emscripten SjLj

Summary:
This makes sure all newly create instructions in Emscripten SjLj has
appropriate debug info attached. Fixes
https://github.com/emscripten-core/emscripten/issues/9797.

Reviewers: kripken

Subscribers: dschuff, aprantl, sbc100, jgravelle-google, hiraditya, sunfish, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74269