[libcxx-commits] [libcxx] [libc++][ranges] Optimize the performance of `ranges::starts_with` (PR #84570)

[Louis Dionne via libcxx-commits]

ldionne wrote:

Note that I don't think this will actually fix #83880 since `ends_with` uses `starts_with` with reverse iterators, and we don't have an optimization for `equal` on reverse iterators.

https://github.com/llvm/llvm-project/pull/84570