[HostStubGen] Add --package-redirect

Example:
--package-redirect dalvik:com.android.hoststubgen.substitution.dalvik

will rewrite all references to classes `dalvik.*` to `com....dalvik.*`.
This allows us to define libcore substitution classes in a different package.
This is useful becuase javac won't let us add classes to the `dalvic` package
which is already taken by the libcore module.

Bug: 292141694
Test: run-all-tests.sh

Change-Id: I01e72f4b4a7ce4baefaaccddbb462edd84267e0e