Break up rasa.core.featurizers.tracker_featurizers into separate modules.

[kedz]

Description of Problem: It was suggested that that rasa/core/featurizers/tracker_featurizers.py is now quite large with the addition of IntentMaxHistoryTrackerFeaturizer and that this module should be broken into smaller modules (see this comment), possibly for each class: TrackerFeaturizer, FullDialogueTrackerFeaturizer, MaxHistoryTrackerFeaturizer, and IntentMaxHistoryTrackerFeaturizer.

In doing so one should also split the corresponding tests in tests/core/featurizers/test_tracker_featurizers.py. Additionally, rasa/core/featurizers/tracker_featurizers/__init__.py should be created which imports all tracker featurizers into the rasa.core.featurizers.tracker_featurizers namespace so that this logic for loading a serialized tracker featurizer is not broken.

[samsucik]

Exalate commented:

samsucik commented:

I think this one is actually blocked by #8798 because the tracker featuriser tests are a mess right now and it makes no sense to split them into featuriser-specific files before they're in a good shape as such.

Definition of done (once #8798 is done) could be:

1. Broke down tracker_featurizers.py into separate modules
2. Added __init__.py to exposes all featurisers and verified that get_featurizer_from_dict works with all
3. Split tests into separate files while ensuring as little code duplication as possible and also ensuring that coverage doesn't decrease for any individual featuriser

[JEM-Mosig]

Exalate commented:

JEM-Mosig commented:

This might become redundant if the disentangling spike yields a plan that we want to go through with.

[stale]

Exalate commented:

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