Remove class aliases from `system` modules

[cesarcoatl]

Is your feature request related to a problem? Please describe.

These class aliases were "necessary" before we added type hints. Now with type hints these are not required as they pollute the stubs package.

Describe the solution you'd like

Take system.util lines 72-73:

PyDataSet = DatasetUtilities.PyDataSet
RequestImpl = SystemUtilities.RequestImpl

Describe alternatives you've considered

Additional context