Implement Hash for MapObserver (#1989)

* MapObserver implements Hash

* Rename the hash utility function (in MapObserver) to hash_easy

* Use hash_slice as a helper function to impl Hash trait

* define_python_map_observer macro implements Hash trait

* Also rename hash_easy to hash_simple

* Rename hash_slice to hash_helper

* hash_helper is used to define the implementation of hash function/trait

* Factor out the Hash trait and function for runtime library structs (#1977)

* Simplify hash_simple (of trait MapObserver) (#1977)

 * Use hash_one function to make hash_simple a one-liner

* remove hash_helper

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Co-authored-by: Edwin Fernando <[email protected]>
Co-authored-by: Addison Crump <[email protected]>

Author: edwin1729