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: I36f49e9546c11ddcddb9968f32169a19516d23f5