[clang] Add some CodeGen tests for CWG 1xx issues (#80338)

Covers CWG issues
[124](https://cplusplus.github.io/CWG/issues/124.html)
[185](https://cplusplus.github.io/CWG/issues/185.html),
[193](https://cplusplus.github.io/CWG/issues/193.html),
[199](https://cplusplus.github.io/CWG/issues/199.html).

I also looked at [190](https://cplusplus.github.io/CWG/issues/190.html),
but concluded that we should try to test it via C++20
`std::is_layout_compatible` first.

I tried to group tests under `dr1xx-codegen.cpp`, but found out that
CodeGen can arbitrarily reorder function definitions in LLVM module. In
particular, interleaving between regular function definitions and
destructor definitions present in the source might not be preserved,
which messes up FileCheck directives. `CHECK-DAG` can help with that,
but its interaction with `CHECK-LABEL` (lack of thereof) would require
me to relax tests too much.