Add package.html files to services metalava stubs

Metalava is reading the package.html files without dependencies,
and sandboxing it without providing package.html causes failures.

Bug: 153703940
Test: m services-stubs.sources services-non-updatable-stubs.sources
Change-Id: I4a34252beb17d8a99db1d630018dfe075ace79ba
1 file changed