add Shell-package-library to allow product type level update

- Car proeducts add additional car permissions to shell package for use cases
  like CTS
- This CL will allow overriding the Shell package rather than adding one
  more package with shared shell uid

Bug: 177099512
Test: Check added package when built in car product.
Change-Id: I6e9103c3275cb2e6df5dc586588eccd7d2ab6b06