AT5-730 implement DeviceTestContext testing for Vcc device

Support was added to allow for testing of a Vcc device without the full kubernetes deployment, using tango DeviceTestContext/MultiDeviceTestContext; this methodology was ported from the project ska-tango-examples.

Implementation functionality does not yet extend to DeviceProxy objects within devices (eg. proxies to VccBand devices inside Vcc), so a workaround was implemented to bypass proxy set up when unit testing. Unit testing thus covers only Vcc commands not invoking internal proxies.

An additional testing script was added to run the Vcc unit tests.