feat: type checking refactor

[pablojhl]

Changes

This makes a refactor of types.py. The main changes are the creation of three new abstractions:

• ScalarType: Base type for all scalar types. It overloads all common functions.
• NumericType: It overloads the function for the numeric types (Integer, PublicInteger, SecretInteger, UnsignedIntegers, ...)
• BooleanType: It overloads the logic functions.

In addition, this adds the terms Mode and BaseType (following the terminology defined in nada-model).

Finally, tests for type checking have been added.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Backwards compatability analysis completed (if applicable). "Will this change require recompilation and upload of user programs?"

[navasvarela]

This is definitely a great leap forward. I have made some comments though. I think the implementation could be further simplified.