Integrate hiddenapi processing into boot jars test

This change registers the hiddenapi singleton so that hiddenapi
processing is performed as part of
TestBootDexJarsFromSourcesAndPrebuilts so that additional hiddenapi
related tests can be added later.

The hiddenapi singleton uses the BootJars/UpdatableBootJars properties
from productVariables not the dexpreopt.GlobalConfig so this change
makes sure that they are consistent.

Performing hiddenapi processing causes the dex file used in "prebuilt
with source apex preferred" test to be encoded with hiddenapi
information which changes the path in the test.

Bug: 178361284
Test: m nothing
Change-Id: I2eb3d8cf11f6fb3bf4a34d6e4ae0c397c890191e