Move openGL check to constructor
Summary: Had to move the openGL check to the constructor and add a rendering test helper member to be called in time.
Test Plan: These are tests
Reviewers: O1 MITK Core, kislinsk
Reviewed By: O1 MITK Core, kislinsk
Maniphest Tasks: T23308
Differential Revision: https://phabricator.mitk.org/D87