[Docstring] Implement Missing Docstrings for verticapy/machine_learning/vertica/base/MulticlassClassifier class

[oualib]

We currently lack docstrings for various base classes in the verticapy/machine_learning/vertica/base/MulticlassClassifier class. It's crucial to have comprehensive documentation to aid users and contributors.

For this one, we need to update all the functions of the different base class. The example should be simple and then refer to the other classes.