Update the methods in BaseUseCase.h

* Remove the streamFrame method
* Rename startVideoStreaming to startVideoStream, as well as
stopVideoStreaming to stopVideoStream, to match the signature in
IEvsCamera
* Add comments for all the methods

Test: build and run on Hawk device
Bug: 130246434
Change-Id: Idf9242207c339142d91c7f7a714eca8fc852972c
diff --git a/evs/support_library/DisplayUseCase.h b/evs/support_library/DisplayUseCase.h
index 19c22c2..4d6f12b 100644
--- a/evs/support_library/DisplayUseCase.h
+++ b/evs/support_library/DisplayUseCase.h
@@ -43,8 +43,8 @@
 class DisplayUseCase : public BaseUseCase {
   public:
     ~DisplayUseCase();
-    bool startVideoStreaming() override;
-    void stopVideoStreaming() override;
+    bool startVideoStream() override;
+    void stopVideoStream() override;
 
     // TODO(b/130246434): Add configuration class to create more use case.
     static DisplayUseCase createDefaultUseCase(string cameraId,