Do not persist entire AutoMLState in Searcher

[Yard1]

Signed-off-by: Antoni Baum antoni.baum@protonmail.com

Why are these changes needed?

Currently, the entire AutoMLState is persisted in Searcher as a part of the config_constraints. As the State object contains the dataframe used, this means a large amount of data will be persisted to disk as a part of automatic Tune Experiment checkpointing, leading to large disk usage and high performance overhead, causing various bottlenecks.

This PR changes the size function used in config_constraints to only consider the learner_classes attribute of AutoMLState which removes the issue of too much data being saved.

Related issue number

Closes #866

Checks

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[sonichi]

Looks good to me. Thanks!