Internal: b/199402891

There are currently ~540 deprecation warnings produced when compiling the engine, most of which are usages of deprecated Android APIs. These should be fixed, and then, the warnings should be made fatal. This issue will serve as a tracker of the issues addressing these deprecations.

*The breakdown currently is ~120 in the engine, ~420 in the engine tests. Note that not all of these deprecations are due to Android APIs; ~60 of the warnings are Robolectric deprecations, ~40 of the warnings are Flutter deprecations, ~30 of these warnings are Dart deprecations, and a couple are junit deprecations.