Partial: ActivityManager: use proc state from compiled aidl

In order to fix divergence in libbinder Android.bp file, adding an
empty file group corresponding to an internal file group.

This is needed to easily manipulate where source files are included
in libbinder without having to land patches internally and externally.

Bug: 183654927
Test: N/A

Merged-In: I3dafe7a75b2dae561583a7821284027a1896b9a5
Change-Id: I8821242efdc0a27daddf30368f948855062f2d14