Show publish plug-in attributes based on families instead of only productType

[BigRoy]

Changelog Description

Show publish plug-in attributes based on families instead of only productType

This PR can be tested together with ynput/ayon-houdini#144

Additional info

This commit 8208bef allows to show publish plugin attributes also based on the created instance families data instead of only the product type. As such, if the Creator defines extra families - then the Pyblish plug-ins for which it will run will now also show their publisher attributes.

This is a required change to easily start supporting a workflow where we can target particular instances from plug-ins without having to target the product type itself. This opens the door to allow say, five different creators, to each produce a model family but with e.g. a different representation - like a USD model, groom, look, etc.

This PR builds on top of #960 so has a much bigger diff than needed (so once that's merged, only then I think it's good to start reviewing the code changes here because it'll reduce the diff drastically.)

📔 ✏️ Houdini (and Maya) currently exposes a get_publish_families method on the Creators - we may want to move that to the base creator plug-in in core by default because it'll greatly simplify the implementation of defining more families than just the product type from a creator across all the DCCs.

Testing notes:

1. Use together with PR here: Allow creating more product types as USD with USD contribution workflow and better defaults. ayon-houdini#144
2. In Houdini, start publishing USD model, groom and look products, each should work with their own validations but also with the asset contribution workflow. Each product should also have different defaults and target the right 'default layer'
3. Regular model publish in Houdini should also still work.

We may need to do a quick simple test across different DCCs that may define families data (at Creation, during publishing shouldn't make a difference) on the instance to see whether they still behave as intended. As far as I know that logic currently only exists inside Houdini and Maya.