Harmonise VQVAE with AutoencoderKL

[Warvito]

Implements #247

[Warvito]

@marksgraham @Ashayp31 @danieltudosiu do you think it is possible to simplify any of these parameters?

        adn_ordering: str = "NDA",
        dropout: tuple | str | float | None = 0.1,
        act: tuple | str | None = "RELU",
        output_act: tuple | str | None = None,

[ericspod]

@marksgraham @Ashayp31 @danieltudosiu do you think it is possible to simplify any of these parameters?

We could have something like ActType = tuple | str | None in a utilities file and act: ActType in the constructor. I would suggest this parameter shouldn't be None ever (nor dropout for which 0.0 should mean no dropout), and we should use the names from the layer factories rather than string literals for the default argument like here. Simplifying the type annotations in MONAI itself is something I had wanted to do a while back now.

[marksgraham]

Hey, looks good apart from the typing issue. Managed to load in some VQ-VAE weights from a model I trained before this PR too (with some minor weights renaming) so all good :)