PackageParser: Parse android:classLoader during the full parse.

There's no need to do this during a "lite" parse. Moreover, we don't
resolve resource references during a lite parse, which means that we
lose a lot of flexibility.

Test: CtsAppSecurityTestCases
Bug: 64339642

Change-Id: I7d02faab6bd226d96d63d2edd8c06b94e15e14ad