Add a `take_any` method

It is not the first time I'm missing a method to remove an arbitrary element from a set or map. This issue has been solved in the standard library for BTreeSet and BTreeMap with the recent introduction of the pop_first and pop_last methods, but there is no equivalent for HashMap/HashSet.

What I'm looking for is as simple as that:

/// Removes an arbitrary element from the set.
fn take_any(&mut self) -> Option

It is currently impossible to remove an element from a HashMap/HashSet through remove or take without a preexisting reference to an element/key of the set/map. So to have such reference the only way is to clone one beforehand:

fn take_any<T: Clone>(set: &mut HashSet<T>) -> Option<T> {
  let result = set.iter().next()?.clone();
  set.remove(&result);
  result
}

It is possible without the Clone bound with the drain_filter that allows to drain the first item and keep the rest, but it seems expansive to me.

fn take_any<T>(set: &mut HashSet<T>) -> Option<T> {
  let mut taken = false;
  set.drain_filter(|_| {
    let take = !taken;
    taken = true;
    take
  }).next()
}

As for the name, it could also be named pop_any to reflect the pop_first and pop_last methods on BTreeSet and BTreeMap.

Review the HashMap and HashSet APIs alongside BTreeSet and BTreeMap's pop_first and pop_last methods, and compare the proposed drain_filter approach. Decide whether take_any or pop_any is the appropriate API, then implement support for removing an arbitrary element without a Clone bound. Done means both collections expose the requested behavior.