[Bug] plugins are imported twice during discovery

[omry]

The examples plugins have something like the following in their __init__.py file:

# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
from .example_searchpath_plugin import ExampleSearchPathPlugin

__all__ = ["ExampleSearchPathPlugin"]

This causes the plugins to be imported twice during plugin discovery, making any slowdown from slow plugin import twice as bad.

This is not necessary and is actually harmful.
This should be fixed in all plugins (official and unofficial).

For official plugins (in the Hydra repository), that __init__.py should be empty:

# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved

[omry]

cc @jrapin

[omry]

cc @jan-matthis