Experimental: Synchronize axes in interactive show diff

[henrikmidtiby]

Overview: What does this pull request change?

This PR improves the interactive window opened by --show_diff when running pytest.
The interactive window can be enabled by installing the pyqt6 python library.

The following things have been changed:

1. The three axes are now synchronized, which makes it easier to compare details in the generated and expected frames
2. The layout have been altered a bit to allow showing the name of the current test
3. The logic for coloring the difference figure is adjusted to handle the case where the expected color value was black but a different value was generated.

How the `--show_diff` view was before the PR.

After enabling synchronized axes and zoomed in on a scene

After adding information about the current test

After changing the difference logic

Motivation and Explanation: Why and how do your changes improve the library?

Links to added or changed documentation pages

Further Information and Comments

Reviewer Checklist

• The PR title is descriptive enough for the changelog, and the PR is labeled correctly
• If applicable: newly added non-private functions and classes have a docstring including a short summary and a PARAMETERS section
• If applicable: newly added functions and classes are tested