[llvm] [WebAssembly] Replace Reachability with SCCs in Irreducible CFG Fixer (PR #179722)

[Petr Penzin via llvm-commits]

https://github.com/ppenzin approved this pull request.

LGTM given fuzzing is passing. @QuantumSegfault thanks for https://github.com/llvm/llvm-project/pull/181254

https://github.com/llvm/llvm-project/pull/179722