[clang] [Clang][Sema] placement new initializes typedef array with correct size (PR #83124)

[via cfe-commits]

dyung wrote:

@mahtohappy the test you added seems to be failing on quite a few buildbots including the documentation build and some x86 ones:
- https://github.com/llvm/llvm-project/actions/runs/8705457952/job/23875893823
- https://lab.llvm.org/buildbot/#/builders/121/builds/40812
- https://lab.llvm.org/buildbot/#/builders/230/builds/27331
- https://lab.llvm.org/buildbot/#/builders/94/builds/19405
- https://lab.llvm.org/buildbot/#/builders/98/builds/36470
- https://lab.llvm.org/buildbot/#/builders/280/builds/1958
- https://lab.llvm.org/buildbot/#/builders/139/builds/63510
- https://lab.llvm.org/buildbot/#/builders/216/builds/37557

https://github.com/llvm/llvm-project/pull/83124