Better redshift icon set

Previous set featuring a lightbulb were too small especially the off status one. The shine around the bulb used up pixels at the top which always forced the bulb into being small.

This new set follows a design with a screen containing a moon or sun to denote night and day modes, and the off icon has both of these plus a cross to indicate an off status.

I also created matching 32px icons which get used in the pop-up notifications panel & the middle on-screen-display bubble.

Screenshots below of current icons (ones I created in !253 (merged)), followed by screenshots of new versions in this merge request. Apologies to be re-doing these, but I'm sure people would complain about the 'off' one in particular, and the on/day ones aren't clear enough for my liking. Note I chose to use solid moon + sun this time as I think these are clearer.

** @teams/vdg**

Edit: fixing title typo from 'reshift' to 'redshift'.