Refactor OpenShiftTestExtension to separate concerns

[Sgitario]

At the moment, the OpenShiftTestExtension is coupling many different purposes:

• Instances Inject (tests and services)
• Initialisation of services
• OpenShift related stuff
• Before and after actions
• Context test store

[Ladicek]

What I personally intended to do (but didn't get to it) is to leave all extension points in a single class (because they all access the same underlying storage), but use some rudimentary dependency injection to move the logic out into separate classes.