[Docs] De/Serializers no longer appear in the API doc

[athewsey]

What did you find confusing? Please describe.

In releases since #3796, the available pre-built Serializer and Deserializer classes are no longer documented in the SDK API doc site. This makes it difficult for users to understand what alternative de/serializers are available (instead of just using the default ones for each framework's Predictor).

Describe how documentation can be improved

In #3796, the pre-built Serializer and Deserializer classes were moved from serializers.py and deserializers.py to base_serializers.py and base_deserializers.py respectively. The Serializers and Deserializers API doc pages used to list these out: For example see the Serializers doc @ v2.150.

However, these new base_* files aren't included in the auto-generated docs.

To improve the docs, we should ensure the available De/Serializer classes are included in the API reference so users can understand what's available.

It may also be worth having explicit guide somewhere mentioning how to override the de/serialization when running estimator.deploy(...), model.deploy(...) or new Predictor(...)?

Additional context

N/A