[clang] [clang-tools-extra] [clang][NFC] Refactor `CXXNewExpr::InitializationStyle` (PR #71322)

[via cfe-commits]

zmodem wrote:

I landed a commit close to this one, and got at least 10 emails about broken buildbots so far (e.g. https://lab.llvm.org/buildbot/#/builders/188/builds/37563). How come presubmit testing isn't catching this? @metaflow 

https://github.com/llvm/llvm-project/pull/71322