[Feature Request]: Add LLVM 22 support

[mcbarton]

Description of new feature

This issue is to track the progress with updating CppInterOp to be compatible with llvm 22. The following things need to be done

• Update native non oop jobs to llvm 22 Add llvm 22 support (native non oop jobs) #812
• Update oop jobs to llvm 22, and drop llvm 20 oop support
• Update Emscripten jobs to llvm 22 Update Emscripten build to llvm 22 #907
• Update cling jobs to llvm 22 (tenative based on root PR updating to llvm 22)
• Drop llvm 19 support Drop llvm 19 support #811
• Update self hosted job to llvm 22 to test cuda support
• Run Ubuntu x86 ci tests under Valgrind
• Enable tests which are broken for llvm 22, despite passing for llvm 21

[mcbarton]

As far as I can tell this error https://github.com/compiler-research/CppInterOp/actions/runs/23491010379/job/68359063882?pr=812#step:13:880 suggests we need a fix upstream in llvm, to pass the GetLanguageStandardC test for llvm 22.

[mcbarton]

Moved to issue description