Add trunk stable flag for exposed AttributionSource constructor

AttributionSource(int, int, String, String, IBinder, String[],
AttributionSource) was exposed as a test api in trunk stable, and
requires a feature flag.

Bug: 304478648
Test: Ran RenouncedPermissionsTest with the flag in both states.
Change-Id: I2a3ab0683bf08a56be2349be466509160ce19f67