Encode the entire class loader context for dex2oat

Until now the split dependencies were passed as a flatten list to dex2oat.
In the presence of DelegateLastClassLoaders this is no longer enough to
ensure the correctness of the compilation.

This CL encodes the split dependencies together with their declared class
loader in a format accepted by dex2oat.

Bug: 38138251
Test: runtest -x
services/tests/servicestests/src/com/android/server/pm/dex/DexoptUtilsTest.java

Change-Id: Iaabd5d8bd5e6d027a8de5a408777fd517063d9f1