Extract SharedPreferences interaction from QSHost

In the new pipeline, use a separate repository to determine/set whether
custom tiles have been added for a given user.

Flag: QS_PIPELINE_NEW_HOST
Test: atest com.android.systemui.qs
Test: manual, add/remove tiles and see the file change
Fixes: 275737462
Change-Id: I94865574c749368bcbb1f1d8743ed8431a25a1e8