Implement special encoding/decoding buffers for maps

[sarvalabs-manish]

• Implement a MapPolorizer and a MapDepolorizer that allow inserting/fetching key-values by random access instead of sorted (ordered) access.
• It will be a wrapper type over the simple encoding/decoding buffers.
• This is useful for implementing custom serialization functions for types that include mapping types and we will temporarily allow this by exporting the map compare and map sorter functions as detailed in Export map sorting & compare functions #31