absl::BlockingCounter vs std::latch

[jiawen]

My team recently migrated to C++20, which features std::latch. std::latch has a superset of the feature set of absl::BlockingCounter. I imagine the STL version is inspired or even built by the same engineers that built the Abseil version.

Mirroring the excellent discussion in absl::Span, I was wondering if Abseil should add a similar discussion highlighting the differences and make recommendations (e.g,. C++ < 20 should use absl::BlockingCounter. We recommend C++ >= 20 to to use ).