feat(setup): improve private status bar

[trueNAHO]

• feat(setup): use more distinctive c.colors.statusbar.private.bg color
  • Make c.colors.statusbar.private.bg more distinctive from c.colors.statusbar.normal.bg by using the darkest palet color. Bright colors are not used because they would make all other c.colors.statusbar properties harder to read.
• feat(setup): create coherent private status bar
  • Using the same color for c.colors.statusbar.command.private.bg and c.colors.statusbar.command.bg assures coherence with other menus, like c.colors.completion.category.bg. However, the overall coherence in private mode is improved by matching c.colors.statusbar.command.private.bg with c.colors.statusbar.private.bg.