refactor: Deprecate array formats and default to dataframe

[eddiebergman]

WIP

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 69.42675% with 48 lines in your changes missing coverage. Please review.

Project coverage is 79.30%. Comparing base (26ae499) to head (6296f37).

Files with missing lines	Patch %	Lines
openml/evaluations/functions.py	36.66%	19 Missing ⚠️
openml/study/functions.py	30.76%	9 Missing ⚠️
openml/datasets/functions.py	61.53%	5 Missing ⚠️
openml/runs/functions.py	78.26%	5 Missing ⚠️
openml/utils.py	80.00%	3 Missing ⚠️
openml/flows/functions.py	81.81%	2 Missing ⚠️
openml/setups/functions.py	93.10%	2 Missing ⚠️
openml/evaluations/evaluation.py	50.00%	1 Missing ⚠️
openml/setups/setup.py	75.00%	1 Missing ⚠️
openml/tasks/functions.py	90.90%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1372      +/-   ##
===========================================
- Coverage    84.19%   79.30%   -4.90%     
===========================================
  Files           38       38              
  Lines         5303     5185     -118     
===========================================
- Hits          4465     4112     -353     
- Misses         838     1073     +235     

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