Set alpha parameter for regularization of `ElasticNetRegression`

[lars-reimann]

Is your feature request related to a problem?

It's not possible to set the alpha parameter for regularization of elastic net regression.

Desired solution

• Add a new parameter alpha: float to the initializer of safeds.ml.regression.ElasticNetRegression
• Raise a value error if alpha < 0
• Warn if alpha == 0 -> Users should use LinearRegression instead
• Pass it along to alpha of the wrapped scikit-learn model in the fit method

Possible alternatives (optional)

No response

Screenshots (optional)

No response

Additional Context (optional)

• Use warnings.warn to warn.
• Use with pytest.warns to test that the warning is created.