Full refactor of Translation APIs.

* Added ViewTranslationRequest/Response
* Added TranslationRequest/ResponseValue
* Removed single TranslationData.
* Moved service.TRequest -> view.TRequest.

Bug: 176208267
Bug: 177371091
Test: atst CtsTranslationTestCases
Change-Id: I25d4bce385d64a8eb9c2a316bd6b5a23e14fb14e