[clang] [Clang][CWG1815] Support lifetime extension of temporary created by aggregate initialization using a default member initializer (PR #87933)

[via cfe-commits]

yronglin wrote:

@zygoloid IIUC, since `CXXDefaultArgExpr` and `CXXDefaultInitExpr` were not added to CFG before and were fall back to constant evaluation in ExprEngine, they were not processed correctly in StaticAnalyzer. 

In CFG:
https://github.com/llvm/llvm-project/blob/63224d717108d927e998da8a67050a6cc5dd74a2/clang/lib/Analysis/CFG.cpp#L2256-L2266

In ExprEngine:
https://github.com/llvm/llvm-project/commit/5f6c173e7cb4f6a74c1aec2af3ae478a995c140d
https://github.com/llvm/llvm-project/blob/63224d717108d927e998da8a67050a6cc5dd74a2/clang/lib/StaticAnalyzer/Core/ExprEngine.cpp#L1965-L2004

I'd like to proposal a separate PR for static analyzer. https://github.com/llvm/llvm-project/pull/91879

https://github.com/llvm/llvm-project/pull/87933