[clang] [Clang] Preserve CXXParenListInitExpr in TreeTransform. (PR #138518)

[Alexander Kornienko via cfe-commits]

alexfh wrote:

Apart from the assertion failure in CodeGen, we have two distinct test cases that started failing after this commit. The code in both cases is sanitizer-clean and looks valid. The failures reproduce with -O0, so it's not about optimizations. Looks like Clang codegen is broken for these cases. Reducing the test cases is not as easy as with Clang assertion failures, but I'll try to produce a test case early next week. So far I just managed to compare x86 assembly produced by clang -O0 without this commit and with it. The diff boils down to a few instances of
```
-       movq    $0, (%rsi)
+       movl    $0, (%rsi)
```

https://github.com/llvm/llvm-project/pull/138518