Deprecate CacheView.iterator in favour of using itertools

[davfsa]

Checklist

• I have run nox and all the pipelines have passed.
• I have made unittests according to the code I have added/modified/deleted.

[FasterSpeeding]

I mean this is still helpful by itself: its more ergonomic if you want to do an async operation over the entries in a cache using an async iterator and collect/iterate over the results rather than directly building an impl of them but it isn't necessary and is arguably misleading so I don't mind getting rid of it.

[davfsa]

That is the idea behind it. In async cache views, the iterator can still be added if needed :)

[FasterSpeeding]

That is the idea behind it. In async cache views, the iterator can still be added if needed :)

Fine by me then