refactor(framework) Convert Driver.pull_messages to no-arg

[chongshenng]

This PR adds the return of an iterator for the Driver.pull_messages().

[panh99]

Both Iterator and list are acceptable types of Iterable. Since we already have a list of messages, we don't need to convert it to an iterator here.

@jafermarq Should we also update the in memory driver so it really returns an iterator and doesn't pull all messages at once? Wdyt?

Suggested change

	def iter_msg() -> Iterator[Message]:
	return iter(message_res_list)
	return iter_msg()
	return message_res_list

[chongshenng]

Should we also update the in memory driver so it really returns an iterator and doesn't pull all messages at once? Wdyt?

Indeed, that was the original idea - to keep the return behaviour the same for both in-memory driver and the grpc_driver.

[chongshenng]

Closing as this is stale.