Replacing 'grunt-svgmin' with 'svgo' v2.3.0.
Also
- replacing all Grunt based tasks with npm equivalents. 'build' has
before just been for SVG minification and that's the same now in npm.
- changing to JS based '.svgo.config.js'
- re-crushing all SVGs. Note that 'link-hover.svg' and 'link.svg' have
been optimized with reduced precision. All other changes are resulting
from updated SVGO.
Bug: T278656
Change-Id: Ie895edb4e88336ffc56f570b8f80bf7d1e331894
