Extension buttons on diffs need redesign work

Created by: rrhyne

Full height extension buttons in the diff views (and other areas where these elements exist) should be redesigned.

For example, the buttons in the panel at the top of diff views should be links instead. Figma:

https://www.figma.com/file/30vUPTo5zeoQXdj5c6478w/Extension-buttons-in-diffs?node-id=0%3A1&viewport=485%2C404%2C0.31086957454681396