[clang] [libc++] Implement ranges::contains_subrange (PR #66963)

[Shafik Yaghmour via cfe-commits]

shafik wrote:

Please make sure you add a description to your PR. This is what usually goes into the git log and we want those entries to be as descriptive and helpful for folks who read the git logs, thank you.

https://github.com/llvm/llvm-project/pull/66963