Add testing support for predictive back animations

Android API 34 officially brought predictive back gestures to the developer platform so that custom animations can be defined. I want to see support for testing the UI state during predictive back animations. This will mean adding interactions for the `started`, `progressed` and `cancelled` actions of back press callbacks.

Start by locating the existing Android back-press testing interactions and the callbacks used for predictive back animations on API 34. Add coverage for the started, progressed, and cancelled actions, and verify that tests can observe the expected UI state throughout those actions.

Written by the indexing model from the issue text.