Remove text from screenshot edit and share icons

Make the screenshot UI more streamlined; also updates the chip
padding for both icon-only and text-and-icon chips.

https://screenshot.googleplex.com/NakbJaCGm6a8iMp

Bug: 184744730
Test: manual; visual verification
Change-Id: Ie07be0c79bf3345fd4433dbaa4779de77f80fedd