[clang] [Clang][AST] {CXXDefaultArgExpr, CXXDefaultInitExpr}::hasRewrittenInit return true iff the init expression was really rebuild (PR #99748)

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https://github.com/Sirraide commented:

Taking another look at this, there’s one thing I’m confused about, but other than that it seems fine.

(Side note in case anyone else gets confused by this: `ASTStmtReader`/`Writer` already (de)serialises this, so no changes are needed there.)

https://github.com/llvm/llvm-project/pull/99748