Merge pull request casper-network#5218 from igor-casper/vm2-collections

Improve collections in the VM2 SDK

Author: igor-casper

smart_contracts/sdk/src/collections.rs

@@ -1,5 +1,7 @@
 mod lookup_key;
 
+mod iterable_map;
+mod iterable_set;
 mod map;
 mod set;
 pub mod sorted_vector;
@@ -8,3 +10,6 @@ mod vector;
 pub use map::Map;
 pub use set::Set;
 pub use vector::Vector;
+
+pub use iterable_map::{IterableMap, IterableMapHash, IterableMapIter, IterableMapPtr};
+pub use iterable_set::IterableSet;