Change BackgroundDexoptJobStatsLogger#write to report packages count

This is needed because of the changes to the BackgroundDexoptJobEnded
atom introduced in ag/24209548 to include the count of optimized packages
and total packages.

Bug: 290340704
Test: atest art_standalone_artd_tests
Test: atest ArtServiceTests
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:dc045dc39537a879b11b8d1e937a7f96a529be90)
Merged-In: I9f27867ed10eaaeb7f8d875f08cc3f82e5015e6b
Change-Id: I9f27867ed10eaaeb7f8d875f08cc3f82e5015e6b