refactor(magnification): Renaming IWindowMagnificationConnection as IMagnificationConnection

Considering the connection is handling functions more than window
magnification operations, we would like to rename it as
IMagnificationconnection.

Bug: 310109308
Test: manually. Renaming the class and methods
      atest IMagnificationConnectionTest
      atest android.view.accessibility.AccessibilityManagerTest
      atest MagnificationTest
      atest CommandQueueTest
      atest com.android.server.accessibility.magnification.FullScreenMagnificationControllerTest
      atest MagnificationConnectionWrapperTest
      atest MagnificationControllerTest
      atest MagnificationConnectionManagerTest
      atest WindowMagnificationGestureHandlerTest
Flag: NA
Change-Id: I6a19621dcf83e3c37b99204631e9bc022e894b5a