Move license module processing to GenerateAndroidBuildActions

Previously, the processing of the license module was done in the
licensesPropertyFlattener method which is called for all modules before
their GenerateAndroidBuildActions method is called. This change moves
the processing into the license module's GenerateAndroidBuildActions
method which was previously empty to match the normal practice.

Bug: 181569894
Test: m nothing
Change-Id: I3736879bfa4b4d1f4e2b35770852a02d09b3db83