Resolve "Update dependencies"

For whoever reviews this: To compile this you need to have qt6 installed and link qwt with qt6. I made some adjustments to the slider (throttling system and better navigation when you click somewhere else on the track. That's why in my opinion it would close #530 (closed) as well). There's also a new docker image (v2). I will update the other CI machines as soon as it is ready to merge.

Reviewer Checklist

General code quality

• naming conventions are met (see .clang-tidy for detailed information)
• no static analyzer warnings in new code parts (e.g., use clang-tidy for checking)

General usability

• old versions of pet-files are still loadable
• documentation updated (if applicable)

Only if changes in UI

• new elements are also saved and loaded from pet-file
• check if tab order is still correct
• all new SpinBoxes are promoted
• new keybindings added to Petrack::keyBindings()

Closes #564 (closed), #530 (closed)