Reduce needless recoverBuilder calls when updating Notification icons

Right now we repeatedly call recoverBuilder through IconManager.updateIcons() which is surprisingly expensive. We call it to resolve the same exact description set for each icon in a Notification. This CL reuses the description and noticably cuts down on repeated description resolution.

Flag: NONE
Bug: 316554966
Test: newly added unit tests and existing tests
Change-Id: Icc4ed9d1890842fa953d1322bcbc941272539355