Cleanup python-objects in aux interface

[sebastianpfischer]

In order to use the different auxiliaries over an exposed interface,

We want to cleanup methods that return a pure python object to more primitive types.

For example:

• https://github.com/eclipse-kiso-testing/kiso-testing/blob/master/src/pykiso/lib/auxiliaries/can_auxiliary/can_auxiliary.py#L133
• https://github.com/eclipse-kiso-testing/kiso-testing/blob/master/src/pykiso/lib/auxiliaries/udsaux/uds_auxiliary.py#L93
• https://github.com/eclipse-kiso-testing/kiso-testing/blob/master/src/pykiso/lib/auxiliaries/ykush_auxiliary.py#L206