Move clear instant app dialog logic out of AppInfoDashboardFragment.

- refactor AppInfoDashboardFragment and move the clear instant app dialog
handling into instant app button controller.
- move the dialog fragment to be a stand-alone class instead of inner
class.

Change-Id: I51c045938f3fd1db73b4b9f7e0311a51df599a29
Fixes: 110102457
Test: make RunSettingsRoboTests