Create a system API to allow preinstalled assistants to receive training data events.

These events are produced during sandboxed detection (within the trusted
process).

Bug: 313702193
Test: atest --no-bazel-mode CtsVoiceInteractionTestCases
API-Coverage-Bug: 291656263
Change-Id: I145ffc721809f82af57527c71be3903e47367645