QML tests - Add minimal files for testing OngoingCallPage

Goal

Having a small minimal test for the OngoingCallPage component So, similar to tests/qml/src/tst_ChatView.qml with:

OngoingCallPage {
        id: uut


        TestCase {
            name: "Foo"
            function test_checkBasicVisibility() {
                // TODO add code to check if end call is visible
            }
        }
    }

Disclaimer

Launching this will probably crash because of required variables (and probably a working CurrentCall).

The Developer will need to add basic structures to be able to launch this.

Definition of Done

Having a working qml_tests with tst_OngoingCall.qml