[llvm] [llc] Register pass plugin callbacks with the new pass manager (PR #217727)

[Xaver Fabian via llvm-commits]

XFabian wrote:

Thanks for the quick revert! The test hardcoded Clang's spelling of an anonymous namespace — getTypeName scrapes __PRETTY_FUNCTION__, which gives (anonymous namespace)::Bye under Clang but {anonymous}::Bye under GCC, so every GCC bot failed. Reland with a compiler-agnostic FileCheck pattern: #218163

https://github.com/llvm/llvm-project/pull/217727