Reschedule bg dexopt job when it's cancelled by API.

Partners may call `cancelBackgroundDexoptJob` in
`OptimizePackagesCallback` to indicate that it's not a good timing to
run the job. In this case, we should reschedule the job.

This CL also changes the stats reporting code to make use of two new
enum values added by https://r.android.com/2311750.

Bug: 255563304
Test: atest ArtServiceTests
Ignore-AOSP-First: ART Services.
Change-Id: Ia15545040e5840974f5ca41eed7f616227180fab
3 files changed