Setup dex load reporter for system server

System server may load code at runtime from outside its original
classpath. In order to ensure this code is optimized (verified) we need to
report it to PackageManager which can optimize it during idle-maintenance
windows.

This CL sets up the reporting infrastructure for system server.

Test: atest DexManagerTest
Bug: 148774920
Change-Id: Ibd2ee38857b97bde426ee0a01c60543f1acb8671