[clang] Reapply "[Clang][CWG1815] Support lifetime extension of temporary created by aggregate initialization using a default member initializer" (PR #92527)

[Erich Keane via cfe-commits]

https://github.com/erichkeane approved this pull request.

I think this looks ok, I'd love it if @cor3ntin took another look, but I'm as happy as before.

https://github.com/llvm/llvm-project/pull/92527