Improve search performance.

The normalization regex is slow (5-10ms per entry on mako), so better
pre-cache it. Also cache the icons, as the number of icons is vastly
smaller than the number of potential search results, so they'll be
reused very often.

The regex change alone brings the duration of a single filter run down
to ~20ms from ~1200ms on mako.

Change-Id: Ia0fa9c554d0d585a52c8a2b87eecbf045388c961