Move AlignmentGridBox out of Control (Gray out calib 5/N)

• Moves ui and code of AlignmentGridBox out of Control into its own class
• Changed GridItem to work with AlignmentGridBox instead of Control

Open question: I started with the std::variant and std::visit, because I though they might be an elegant solution, but I don't know if it is that much more elegant; it seems a bit clunky to use. So any comments on that would be highly appreciated.

Related #277 (closed)

Reviewer Checklist

Formatting

• the pre-build checks succeed

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

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()