Remove utopya transform function

With !48 (merged), data transformations will be possible entirely via the dantro DAG framework and in a much more versatile fashion than utopya.dataprocessing.transform allows.

To not duplicate that functionality, we should remove it from utopya. This will make the interface clearer and reduce code redundancy.

Tasks

1. #224 (closed): Implement DAG-based alternatives to the currently implemented plotting functions
2. Deprecate the existing utopya transform function
3. Make operations missing from dantro operations database available
   • Make a list in this issue which ones those are
   • Consider moving general operations over to dantro
   • For special operations: register them on utopya-side via register_operation
4. Migrate any plotting functions relying on the utopya transform function
5. Remove the transform function from utopya

People involved

@herdeanu @blsqr @jeremiastraub

Related issues

• #96 (closed)
• #44 (closed) alleviated by this