Fixed Live Preview tooltip styling.
Merge pull request #8720 from adobe/rlim/parse-less-and-scss

Parse less and scss files
Address all the late feedback that came in after the merge.
Removed "Working Files" text-shadow because it's a label.
Made it so that text isn't visible when Working Files settings icon is on top of "Working Files" label.
Using the right highlight value for dark primary buttons.
Dropdown triangles should look like equilateral triangles like all the other triangles.
Tweaked File Type Switcher triangle spacing and dimmed the triangle colors for better a visual hierarchy (button labels need to stand out a little bit more).
Added no-editor background image for dark UI.
Added 3px spacing between "Update" and "Remove" button in Extension Manager.
Tweaked quiet text color. It's not supposed to be the same as light UI's color.
Made the extension manager info text quieter to break the UI up a bit.
Dark spinner needed to be more saturated.
Fix for #8817.
Removed "bevels" on selection bar.
Removed dark styles from side bar as dark styles aren't needed in the side bar.
Fix for #8808.
Tweaked Themes icon because its label was 1px off the baseline.
Fixed dark UI active line styling and behavior.
Fix for #8855.