[hydra-configs-torch][tests] Optimizers and LR schedulers

[romesco]

https://github.com/facebookresearch/hydra-torch/blob/691a390abd2edf764f9431a56b8058ff2c12eb0c/tests/test_instantiate.py#L40

Check minimal tests. Is this the right way to confirm our configs instantiate the correct object?

From previous PR discussion:

Ideally I wanted these tests to do 3 things:

1. Ensure the config exists.
2. Be a valid input to instantiate (and subsequently get an object back).
3. Show that this object works as expected.

For an optimizer, taking a step seems to prove that it is functioning correctly. Comparing the output of your cfg optimizer and a directly called optimizer is kind of a bonus in that if it didn't work, it doesn't mean we didn't instantiate an optimizer correctly given the config. It just means the optimizer has nondeterministic behavior.

[romesco]

Need to complete LR schedulers as well.