Redesign parameter handling

[nwittler]

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

Describe the solution you'd like Previously parameters of both model and control components were managed in a object.params dictionary. This should be modified so that the property is directly a field of the object. E.g. qubit.params["frequency"] becomes qubit.frequency. Example: https://github.com/q-optimize/c3/blob/ef9533008dccbcb23810e1e7396f85b5f200da15/c3/system/chip.py#L77-L99

For this to work each object needs to implement a get_parameters() method that exposes properties to the parametermap to be used instead of comp.params.items() in the following: https://github.com/q-optimize/c3/blob/ef9533008dccbcb23810e1e7396f85b5f200da15/c3/parametermap.py#L38-L45

Describe alternatives you've considered

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