Use `consumer` generator method decorator to attach type annotations to created generator.

[cboulay]

I'm working on a function to check that a chain of processors all have compatible message types. For new processors, this works fine. It breaks down when one of the processors in the chain is an older processor using a generator. It's possible but unreliable to get the generator's origin method's signature from a globals lookup. A preferable solution would be to attach the annotations directly to the generator when it is created from the generator function when the annotations are easily accessible. This isn't very difficult in ezmsg because we almost always decorate our generator methods. Something like the following might allow the type annotations to be attached to the created generator.

Possible change:

def consumer(func):
    @functools.wraps(func)
    def wrapper(*args, **kwargs):
        gen = func(*args, **kwargs)
        # Extract type hints from the generator function
        ret_type = typing.get_type_hints(func).get('return')
        if ret_type and hasattr(ret_type, "__origin__") and ret_type.__origin__ is typing.Generator:
            gen_args = typing.get_args(ret_type)
            if len(gen_args) >= 2:
                # Attach type information directly to the generator instance
                gen._generator_types = (gen_args[0], gen_args[1])
        next(gen)  # Prime the generator
        return gen
    return wrapper