refactoring Arr and Iter

[azjezz]

Arr and Iter components are currently confusing, with some functions being pure, and other not, some returning lists, dicts, or just a value/key, or something else.

The idea would be:

1. Iter would contain generic array functions that operate on all iterables, and usually don't return an iterable ( e.g: Iter\first, Iter\count, Iter\contains, Iter\contains_key .. etc )
2. a new component Vec should contain every function that returns a vec ( i.e list ) from both Arr and Iter.
3. a new component Dict should contain every function that returns a dict ( i.e array<Tk, Tv> ) from both Arr and Iter
4. deprecate Arr component ( all functions will be move to either Iter, Vec, or Dict )

This also means that we lazy loaded iterators, however, i don't see that as an issue, most functions will still accept iterables, so you can provide a generate, and wrap the result in a generator your self.

However, this doesn't solve the pure issue, where functions are not considered pure, but after #119, we can extend the psalm plugin to make it so Vec\sort($array) considered pure, while Vec\sort($db->getUsers()) ( where $db->getUsers() returns a mutable traversal ) considered impure.

[azjezz]

deprecation will take place in 1.2, and the removal of old functions will happen in 2.0.

[azjezz]

done in #241