DO NOT MERGE - Disallow deletion of channels with FGS notifications

Bug: 156090809
Test: atest CtsAppTestCases:NotificationManagerTest
Test: atest CtsAppTestCases:android.app.cts.ServiceTest
Change-Id: I1c2bb78d86f194585d273661cecf3419f51965df
Merged-In: Ie917a4d1b4595a576c4ea5ea079ecc773000abdc
(cherry picked from commit b320763eb82eb81e42df5b649658b78742ad0b5e)
5 files changed