feat: hyperparameter optimization for RNNs and CNNs

[sibre28]

Closes #912

Summary of Changes

New Features:

• fit_by_exhaustive_search now also works for RNNs and CNNs
• ClassificationMetrics and RegressionMetrics now also work for TimeSeriesDatasets, even when the predictions are of type list.
• Raise Error when classifing time series data with continuous = True, as we dont currently support this use-case (since both classification and continuous predictions require the amount of neurons in the last layer to be set differently, according to either the number of classes or the number of values to predict; The output would have to be 2-dimensional)

[github-actions]

🦙 MegaLinter status: ✅ SUCCESS

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ PYTHON	black	5	0	0	1.67s
✅ PYTHON	mypy	5		0	3.62s
✅ PYTHON	ruff	5	0	0	0.36s
✅ REPOSITORY	git_diff	yes		no	0.35s

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[codecov]

Codecov Report

Attention: Patch coverage is 99.26740% with 2 lines in your changes missing coverage. Please review.

Project coverage is 98.17%. Comparing base (ccb60c3) to head (76b78ca).
Report is 32 commits behind head on main.

Files with missing lines	Patch %	Lines
src/safeds/ml/nn/_model.py	99.11%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #923      +/-   ##
==========================================
+ Coverage   98.14%   98.17%   +0.03%     
==========================================
  Files         122      122              
  Lines        6958     7183     +225     
==========================================
+ Hits         6829     7052     +223     
- Misses        129      131       +2     

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[lars-reimann]

🎉 This PR is included in version 0.28.0 🎉

The release is available on:

• v0.28.0
• GitHub release

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