[clang] [mlir] [libcxx] [llvm] [clang-tools-extra] [libc++][concepts] Implements concept helper `__libcpp_integer` (PR #78086)

[Mark de Wever via llvm-commits]

https://github.com/mordante approved this pull request.

LGTM! Thanks! Please ping me when you've update your other patch with these changes.

https://github.com/llvm/llvm-project/pull/78086