Rename TSDataset methods: add_columns_from_pandas -> add_features_from_pandas, update_columns_from_pandas -> update_features_from_pandas

[d-a-bunin]

🚀 Task description

Current names are suggesting inner structure.

Plan

• Rename method TSDataset.add_columns_from_pandas -> TSDataset.add_features_from_pandas
• Rename method TSDataset.update_columns_from_pandas -> TSDataset.update_columns_from_pandas
• Replace all usuages of old names

Test cases

• Fix tests after changing names

Additional context

Discussed in #435

[ArtemLiA]

Hi! I would like to do this, unless, of course, someone else is doing it now.

[d-a-bunin]

I'm assigning you to this task for now. It will be reassigned if time will come to finish the milestone in a short amount of time.

[d-a-bunin]

Closed by #593.