For the sake of consistency across all dialogs and window that behave
like dialogs, remove the static line that separates the main part of
the dialog from the standard buttons. This only applies to windows
that have the standard button on the bottom of the frame.
This covers the 3D viewer, CvPcb, common, GerbView and KiCad dialogs.
Add a reset button that will only show up if the user
edits the JSON configuration for grids. This is a temporary
measure until we have a real grid editor GUI in V7.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/7595