[clang] [NFC][clang][Modules] Add regression test for implicit lambda capture from merged module copies (PR #222020)

[Adarsh Mishra via cfe-commits]

Adarsh-Me wrote:

The red on `609cb782` is infra, not this diff. Only one target fails: `check-cross-project` -- 66 dexter tests, all with `AttributeError: module 'yaml' has no attribute 'CLoader'`, i.e. PyYAML without libyaml on the runner. The other three lit suites report no failures. #224349 names this symptom and landed 09-17; this head predates it. Want a rebase?


https://github.com/llvm/llvm-project/pull/222020