Allow start of explicit intents

This change relaxes startActivity* logic to allow for all explicit
intents to be started, even if the package name provided for such intent
is not visible to the caller.

Fixes: 161007330
Bug: 148657387
Test: atest AppEnumerationTests
Change-Id: Iceaee276e8d4c297ace1fe605100f52e4cc49b07