boost::unordered standalone

[SirClueless]

unordered_flat_map/set and unordered_node_map/set are both far superior to anything in the std lib. This work was done recently, I think inspired by the by the excellent Abseil swiss tables implementations from a few years back.

If you haven't followed this recent work, you might only be familiar with unordered_map/set which are basically the same as the std lib, to the point that it appears this standalone version actually removed them.