T29572 Fixed Tool_interation_multi_dpi_monitor

Summary: Fixed T29572

Test Plan:
test on different OS with multi monitor setup (with different DPI)

1. load an image
2. click into the render windows -> crosshair should move to the clicked position
3. move application to screen with different DPI
4. redo 2 -> should still work correctly.

Reviewers: O3 MITK Reviewer Group II, O1 MITK Reviewer Group I, kislinsk

Reviewed By: O3 MITK Reviewer Group II, O1 MITK Reviewer Group I, kislinsk

Subscribers: a178n, kislinsk

Maniphest Tasks: T29572

Differential Revision: https://phabricator.mitk.org/D825