Introduce an interface to listen to user actions while uninstalling

Every dialog  will use this interface to pass user actions to the view. Implementations of these abstract methods will be done in subsequent changes.

Bug: 182205982
Test: builds successfully
Test: No CTS Tests. Flag to use new app is turned off by default

Change-Id: Ib85867b82267a62937cce77c80bc3b1c4f6b085e