Preopt APEX system server jars.

The path to the artifacts will in the form of
/system/framework/oat/<arch>/<encoded-jar-path>@classes.{odex,vdex,art},
where <encoded-jar-path> is the path to the jar file with "/" replaced
by "@". For example,
/system/framework/oat/x86_64/apex@com.android.art@javalib@service-art.jar@classes.odex

There will be a follow-up CL to update ART runtime to recognize
artifacts in that path.

Test: m com.android.art
Bug: 194150908
Change-Id: Ic89fd63c4b1cd565684cead83fc91dae3bc97a4c