gh-130992: Add Interface Enforcement to abc Module

[programadorLhama]

Description
This PR introduces a new InterfaceMeta metaclass in the abc module, enabling strict enforcement of interface method signatures in Python.

Motivation
Python's abc module allows for defining Abstract Base Classes (ABCs) but does not enforce method signatures. This can lead to subtle runtime errors if a derived class implements a method with an incorrect signature.

This PR adds an InterfaceMeta metaclass that ensures:

• All required methods in an interface are implemented by derived classes.
• Method signatures match exactly (parameters and return type annotations).
• A TypeError is raised at class definition time if any method is missing or incorrect.

Changes Introduced

• New Metaclass: InterfaceMeta (extends ABCMeta).
• New Base Class: Interface, allowing strict interface enforcement.

Example Usage

from abc import Interface

class MyInterface(Interface):
    def method(self, x: int) -> str:
        pass

class ValidImplementation(MyInterface):
    def method(self, x: int) -> str:
        return str(x)

class InvalidImplementation(MyInterface):
    def method(self, x):  # Missing return annotation
        return str(x)

# Raises TypeError: "Method 'method' in class 'InvalidImplementation' does not match the interface signature."
# Expected: (self, x: int) -> str
# Got: (self, x)

Issue Number
Closes gh-130992

Performance Impact
Minimal, as the verification occurs only at class definition time.

Backward Compatibility

• Does not modify existing ABCMeta behavior.
• Codebases using ABC remain unchanged.

Alternative Approaches Considered

• Extending ABCMeta with optional signature enforcement.
• Using static type checkers (mypy), which do not enforce runtime correctness.

Open Questions

• Should this be integrated directly into ABCMeta, or remain a separate base class (Interface)?
• Should return type enforcement be optional?

Documentation Updates

• The abc module documentation should include an example of InterfaceMeta.

Tests Added

• Unit tests verifying:
  • Correct enforcement of method names and signatures.
  • Raising TypeError for incorrect implementations.

Next Steps

• Review and discussion on whether this should be included in the standard library or proposed as a PEP.

🚀 This PR enhances Python’s OOP capabilities by introducing strict interface enforcement, improving maintainability and reducing runtime errors.

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[ZeroIntensity]

See my comment in the (now closed) issue.