[llvm] `dwarf2yaml.cpp` optimizations (PR #179048)

[via llvm-commits]

stevenwdv wrote:

@jh7370 Yes. The dwarf2yaml part was significant but definitely not the only optimization. How do you want me to benchmark? As mentioned, this LLVM version seems newer than what the modified Binaryen version was based on and contains more copies than it does, although the Binayen version has extra copies other places. Do you want me to add some of the LLVM copies to the Binaryen version of the main branch, although that will not be entirely accurate, or just compare with the version from the main branch, which is less representative for this PR?

https://github.com/llvm/llvm-project/pull/179048