[clang] [SemaCXX] Implement CWG2351 `void{}` (PR #78060)

[Mital Ashok via cfe-commits]

MitalAshok wrote:

Initializer list syntax isn't available in C++98 mode (even as an extension? I can't find the option)  
Even so, as a defect report it should apply to all prior C++ versions.

https://github.com/llvm/llvm-project/pull/78060