Support async contextmanagers in contextlib.suppress

[Nineteendo (Nice Zombies)]

This was also proposed:

@rrolls

with (
    async acquire_lock() as lock,
    open('config.json') as f,
    async connect_to_db() as db,
    temp_directory() as tmpdir,
):

Then you could have this:

with (
    suppress(FileNotFoundError),
    async aiofiles.open("config.json") as f
):