Stock collection support for IMapView

[kennykerr]

Building on #2350 and as part of #91, this update adds a stock implementation of IMapView<T>. You can now write the following:

let map = BTreeMap::from([(1, 10), (2, 20), (3, 30)]);
let map: IMapView<i32, u64> = map.try_into()?;

Fixes: #91