[Feature Request] Make sure that all losses work with tensorclasses and regular tensors

[vmoens]

Motivation

We should add tests for all losses with

• [ ] tensors passed via tensordict.nn.dispatch. This should be accompanied by an example in the docstrings of how to use the losses without tensordict.
• [ ] Similarly, it should be easy to pass regular nn.Modules to the losses (eg an actor that reads an obs and outputs an action, a qvalue that reads an obs and an action and outputs a value, etc).
• [ ] We also need to check that losses work with tensorclasses. This essentially requires us to check that no __getitem__ is used for get(key), ie the latter should always be preferred. Tests should all include a tensorclass version.

[andrewldesousa]

hey @vmoens is this still a relevant issue? if so i can look into it this weekend

[vmoens]

Yeah I don't think we really test that!