Add functionality to the QueueView / SetView.

[MathieuDutSik]

Motivation

The QueueView has front / delete_front while we may want to have a pop.
The SetView also has the contains / remove, and we may want to do both at once.

Proposal

Implement a .pop() for QueueView. Implement a remove_if_present for SetView.

Unfortunately, the front is not systematically followed by a delete_front. So, we cannot use it in the code.
For the SetView change, another PR indicates a different direction: Altogether removal of the unskippable entries.

Test Plan

CI. Unit tests have been added.

Release Plan

Not that important. Could be

Links

None.

[ma2bd]

Do we need this API?

[MathieuDutSik]

It turns out no. That being said it is the standard usage of queues.

[bart-linera]

Instead of adding remove_if_present, wouldn't it make more sense for remove to return a boolean, indicating whether the value was present? That's how BTreeSet and HashSet work, at least.

[MathieuDutSik]

Instead of adding remove_if_present, wouldn't it make more sense for remove to return a boolean, indicating whether the value was present? That's how BTreeSet and HashSet work, at least.

We could of course do that. But fn remove is not async and does not even return an error. So, it is quite a useful idea to still have both forms even if their name could change from the ones we have now.