Summary:
After showing and closing the context menu by right-clicking in
{nav View} mode, the cursor would be set to `ClosedHandCursor`. Only
after another click the cursor would be set back to the regular
`OpenHandCursor`.

The issue can be fixed by not changing the cursor shape in the first
place for showing the context menu, i.e. when right-clicking.

While using the {nav Red Eye Reduction} tool, the patch will prevent
the unwanted placement of corrections on the canvas when right-clicking.

{nav Fullscreen} mode could be toggled by double-clicking the middle
mouse button, but it should only work for the left button.

Test Plan:
Right-click on an image in {nav View} mode to show the context menu and
dismiss it again. The cursor should look as before. Also try right-clicking
over the Bird's eye view and in the {nav Crop} tool.

In the {nav Red Eye Reduction} tool, right-clicking should not change the
position of the correction anymore.

Entering {nav Fullscreen} should only work for double-clicking with the left
mouse button. Note that accidentally clicking on the {nav Fullscreen} checkbox
of the context menu when right-clicking and moving the cursor slightly
might still be possible, but having that action as the first entry is
more important than the very minor imperfection in that case.

Reviewers: #gwenview, huoni

Reviewed By: #gwenview, huoni

Subscribers: huoni

Differential Revision: https://phabricator.kde.org/D13723