App Installation API

Is your feature request related to a problem? Please describe.
Some applications check the installer package information at runtime to check whether they have been installed by the Google Play Store, namely every app that uses DexGuard implements such checks.
Moreover, there are many alternative stores such as F-Droid, Aurora Store and Aurora Droid which implement background app installation via their own privileged services.

Describe the solution you'd like
I'd like for FakeStore (or similar application) to implement an API that lets alternative stores install applications in the background, so that the installed applications will see com.android.vending as their own installer

Describe alternatives you've considered
The installer package can be set while installing with pm in an adb shell, while both F-Droid, Aurora Store and Droid have their own Services that have to be installed as a System Application in order for them to work

Review the FakeStore installation flow and the requested background-installation behavior described in the issue. Compare the needs of F-Droid, Aurora Store, and Aurora Droid with Android's installer-package handling and privileged-service constraints. Done means an alternative store can install an application in the background while the installed application observes com.android.vending as its installer.