Simplify set and inline set design

[geeknoid]

Right now, the sets/* and inline_sets/* types mirror the types in maps/* and inline_maps/*. It should be possible to support all the needed use scenarios for sets by implementing fewer types and leveraging generics instead. In particular:

sets/binary_search_set.rs
sets/eytzinger_search_set.rs
sets/dense_scalar_lookup_set.rs
sets/scan_set.rs
sets/ordered_scan_set.rs
sets/hash_set.rs

And the similarly-named types from inline_sets could be replaced with:

sets\hashed_set.rs
sets\ordered_set.rs
sets\scalar_set.rs
sets\string_set.rs

Accepting a generic Map<K, V> as a constructor parameter.