Made following changes to Settings:

- Moved the Voice Input setting from Digital assistant app to Languages & input.
- Bundled Voice Input and Text-to-speech settings together under Speech
  category.

Bug: 218609449

Test: refactoring CL. Existing unit tests still pass.
Change-Id: I3107a410ed35685f5f1081cbe448b105b5c79c24

src/com/android/settings/applications/assist/ManageAssist.java

@@ -73,7 +73,6 @@ public class ManageAssist extends DashboardFragment {
         controllers.add(new AssistContextPreferenceController(context, lifecycle));
         controllers.add(new AssistScreenshotPreferenceController(context, lifecycle));
         controllers.add(new AssistFlashScreenPreferenceController(context, lifecycle));
-        controllers.add(new DefaultVoiceInputPreferenceController(context, lifecycle));
         return controllers;
     }