If we keep doing design validations at two different places, they can
only start to drift apart. Board Setup should validate for malformed
data ONLY; everything else is the business of DRC.
This also fixes a bug where implementation validations would not allow
OK in the dialog, but wouldn't put up a message to say why. We now use
the InfoBar impl from Jon's commit for that.
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
Jeff Young
Jon Evans
Mark Roszko
Ian McInerney