Cache IconImage for feeds on the Feeds screen.
Cache IconImage for feeds on the Feeds screen.

Empty the cache, and reload visible cells, when the trait collection changes, so that we get the proper icons for light/dark mode. This caching provides a small-but-worthwhile performance increase for the Feeds screen.

brentsimmons/Evergreen,brentsimmons/Evergreen,brentsimmons/Evergreen,brentsimmons/Evergreen