hwui: improve RenderThread jank classificaion

Mark UI frames that didn't make it to their expected presentation
due to RenderThread animations as dropped.

Screenshot from Perfetto: https://screenshot.googleplex.com/3pQuNaDYAhHLYu7

Bug: 210605870
Test: manual
Change-Id: I709b2bacbafb8027d97f2fcc39831de7735fc3ff