[Sb refactor] show data activity in Mobile view

Adds support for reading the config `config_showActivity`, and uses the
new `DataActivityModel` type to show the data activity in the mobile
view model / view binder

Test: MobileIconViewModelTest
Test: MobileConnectionRepositoryTest
Test: DemoMobileConnectionParameterizedTest
Test: manual demo mode
Bug: 238425913
Change-Id: Id413d57d6c694ea6f324b022f6d215ae71b22074