refactor: create abstract base classes Classifier and Regressor for supervised models

[lars-reimann]

Closes #60.

Summary of Changes

• Create abstract base class Classifier and make all current classifiers subclasses of it
• Create abstract base class Regressor and make all current regressors subclasses of it.

[codecov]

Codecov Report

Merging #66 (30e2102) into main (db6dbd7) will increase coverage by 0.24%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #66      +/-   ##
==========================================
+ Coverage   91.48%   91.73%   +0.24%     
==========================================
  Files          44       46       +2     
  Lines        1128     1161      +33     
==========================================
+ Hits         1032     1065      +33     
  Misses         96       96              

Impacted Files	Coverage Δ
src/safeds/ml/classification/__init__.py	100.00% <100.00%> (ø)
src/safeds/ml/classification/_ada_boost.py	100.00% <100.00%> (ø)
src/safeds/ml/classification/_classifier.py	100.00% <100.00%> (ø)
src/safeds/ml/classification/_decision_tree.py	100.00% <100.00%> (ø)
...lassification/_gradient_boosting_classification.py	100.00% <100.00%> (ø)
...c/safeds/ml/classification/_k_nearest_neighbors.py	100.00% <100.00%> (ø)
...c/safeds/ml/classification/_logistic_regression.py	100.00% <100.00%> (ø)
src/safeds/ml/classification/_random_forest.py	100.00% <100.00%> (ø)
src/safeds/ml/regression/__init__.py	100.00% <100.00%> (ø)
src/safeds/ml/regression/_ada_boost.py	100.00% <100.00%> (ø)
... and 9 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[lars-reimann]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ PYTHON	black	19	0	0	0.73s
✅ PYTHON	flake8	19		0	0.52s
✅ PYTHON	isort	19	0	0	0.26s
✅ PYTHON	mypy	19		0	2.01s
✅ PYTHON	pylint	19		0	2.3s
✅ REPOSITORY	git_diff	yes		no	0.03s

See detailed report in MegaLinter reports
Set VALIDATE_ALL_CODEBASE: true in mega-linter.yml to validate all sources, not only the diff

MegaLinter is graciously provided by

[lars-reimann]

🎉 This PR is included in version 0.3.0 🎉

The release is available on:

• v0.3.0
• GitHub release

Your semantic-release bot 📦🚀