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

[Mital Ashok via cfe-commits]

MitalAshok wrote:

@zygoloid The commit message was a bit outdated, it now takes the void type from `T` instead of the initializer list (this also preserves extra info like if it came from a typedef)

I've also changed it to `CK_ToVoid`

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