Add contract name to exceptions

[iamdefinitelyahuman]

What I did

• Display the name of the active contract when raising an exception. This is useful when an exception occurs while parsing an interface.
• Ensure the correct annotation shows when parsing interfaces.

How I did it

• Add a name field to the Module AST node. This gets added via a new kwarg for parse_to_ast
• Include the contract_name kwarg when generating ASTs in compiler and signatures

How to verify it

Cause an exception. It should give output like this:

UnknownType: Not a valid type - value is undeclared
contract "cERC20", function "transfer", line 21:18 
     20 @external
---> 21 def transfer(_to: oopsie, _value: uint256) -> bool:
--------------------------^
     22     pass

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