Shortcut integration with AppSearch (Part 5)

Following changes are implemented in this CL:
1. Persist shortcuts to icing whenever a shortcut is created/updated.
2. Delete shortcuts from icing only when publisher explicitly removes
the shortcut. i.e. deletion due to exceeding shortcut limit / disabling
shortcut do not lead to shortcut deletion from icing.
3. Call AppSearchSession#reportUsage when
ShortcutManger#pushDynamicShortcuts is invoked.
4. Add StrictMode warning for calling async method on mainthread.

Bug: 151359749
Test: atest ShortcutManagerTest1 ShortcutManagerTest2 ShortcutManagerTest3 ShortcutManagerTest4 ShortcutManagerTest5 ShortcutManagerTest6 ShortcutManagerTest7 ShortcutManagerTest8 ShortcutManagerTest9 ShortcutManagerTest10 ShortcutManagerTest11
Test: atest CtsShortcutManagerTestCases
Change-Id: I7ae7ec50a7e49f8de819d8239d429fc494017f96