For some kinds of issues, we want a way to point them out but
we don't need to keep the user from being able to close the
dialog. A separate Validate button lets the user check for
issues if desired, but these issues are not "fatal" and can
be ignored if the user wishes.
Display warning infobar in the board/schematic setup when no project
is loaded, since most of the settings in those dialogs are saved in
the project and not in the board/schematic file.
Fixes https://gitlab.com/kicad/code/kicad/-/issues/4868
Jon Evans
Jeff Young
Mark Roszko
Ian McInerney