[clang] [clang-tools-extra] [compiler-rt] [flang] [lld] [lldb] [llvm] [mlir] [openmp] Treewide C++26/2d fixes (PR #223284)

[via llvm-commits]

rdong8 wrote:

Ok, I've separated the non-mechanical fixes into these two PRs:
- https://github.com/llvm/llvm-project/pull/226743
- https://github.com/llvm/llvm-project/pull/226834

https://github.com/llvm/llvm-project/pull/223284