Clean up ArtClassDefinition

This struct was somewhat messy. Clean it up and consolidate functions
into it.

Bug: 31455788
Test: ./test.py --host -j40

Change-Id: Ia3abe92dcf3313677de5e200f673252f8e41d69e
(cherry picked from commit b7354d5bc76ed3975af636f87aa953f8a4d308a9)
7 files changed