[clang] [Clang] Add test for base class init through a conversion function (PR #232902)

[via cfe-commits]

Glitch-On wrote:

@shafik I should mention that I used an AI tool while writing this test, which I missed is not allowed for good first issues. Sorry about that. I'm fine closing this pr and leave it to you.

https://github.com/llvm/llvm-project/pull/232902