Simplified override api

[maldoinc]

After

from wireup import qualified

with container.override({
    RandomService: random_mock,
    qualified(Database, qualifier="readonly"): db_mock,
}): ...

Before

with container.override.injectable(target=RandomService, new=random_mock):
    response = client.get("/random")

from wireup import InjectableOverride

overrides = [
    InjectableOverride(target=UserService, new=user_service_mock),
    InjectableOverride(target=OrderService, new=order_service_mock),
]

with container.override.injectables(overrides=overrides):
    response = client.get("/checkout")