Deprecate range to range_raw

[maurolacy]

After #432, we'll have full range deserialization working for Map.

Let's deprecate range in favour of range_de, keeping range as range_raw.

Regarding prefix vs. prefix_de, let's (try to) keep prefix_de as prefix, and remove the current prefix. That is, no prefix_raw impl, which will be confusing. That implies making range_raw work with / over prefix_de.

This also includes migrating the code in contracts to take advantage of the new key deserialization when useful.

Also, as part of this, let's improve traits segregation over Map and Prefix range-related methods, so that trait bounds are enforced only when strictly needed.

[ethanfrey]

I support this.
I would target 0.11 for this, and get the new features in 0.10, so people can start opt-ing in.