Address API review comments on HotwordTrainingData.

1. Add units to max training data size.
2. Rename mTrainingAudios to mTrainingAudioList.
3. Convert mTimeoutStage from an IntDef to a generic integer.

Test: atest --no-bazel-mode
CtsVoiceInteractionTestCases:HotwordTrainingDataTest
Change-Id: I71e97e83d0c08a6207ed485e175acdeb171df5a4
Bug: 298094222
3 files changed