menuconfig: Show menus with unsatisfied 'visible if' in red in show-all mode
menuconfig: Show menus with unsatisfied 'visible if' in red in show-all mode

Previously they were shown in white, due to an oversight in
_draw_main().

_draw_main() should use the same logic as _shown_nodes(). Move it into a
separate _visible() function and call it from both.

ulfalizer/Kconfiglib,ulfalizer/Kconfiglib