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

[Aaron Ballman via llvm-commits]

https://github.com/AaronBallman requested changes to this pull request.

This is a massive PR for very little benefit; we will not be enabling C++26 mode in tree for a *long* time (we're still not yet comfortable enabling C++20 in tree, so C++26 is likely 10+ years away).

At the very least, this needs to be split into multiple PRs but I also question the value of the changes to the community.

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