Add Sideloaded detector

A helper class to detect if any package is unsafe or sideloaded.
A package is considered unsafe if not a system app and not installed
through trusted sources.
The usage will be added in the following cls.

Bug: 154263570
Test: Added UnitTest
Change-Id: Ifffbe64ae95029427aeca4a997bc440dbdc2d3d6
3 files changed