Added Repository for emitting user installed apps:

1. This Repo is User Aware
2. This repo reacts to changes in installed applications(removing/adding
   an app)
3. This repo only emits apps that are visible to the user, i.e. System
   Apps, or apps not visible in Launcher's All Apps will not be shown.

Fix: 403243843
Flag: com.android.systemui.extended_apps_shortcut_category
Test: UserVisibleAppsRepositoryTest
Change-Id: I794d4b1d58b614dc95c87ee616f6ed3635d18a7e