Update icons

[craigcook]

We have a whole new icon set! It comes in two different sizes/weights. We need to add them as optimized SVGs in both black and white, and might need to think about how to organize them... maybe a folder for each size and color, or just put them all in one folder and follow a naming convention?

This will be a breaking change. Depending on how we decide to organize them I expect paths and filenames will change. Many are direct replacements for existing icons but others are new, and some existing icons will be deleted.

[maureenlholland]

+1 for the idea of weight & color folders (icons/solid/black, icons/outline/white)

Allows file names to stay concise and easier to update if we decide we want to change a name (one folder vs many hyphenated files)