This updates our accent styling colors for info, success, error,

warning, and highlight based on the alert colors, and adds outline

colors for each.
Alerts are updated to use these, ensuring they're consistent with any

other UI elements that want to use the same color.
In the process, I've updated the info and success accent colors to look

the same on both light and dark modes. Since these are important bits of

information, and not too bright in light mode, I think this is suitable

for now, and avoids a muddy look.

Tested these in Storybook and in Review Board.