Fix DragDividerToResize flicker tests

Update the proper steps number for testing split resizing.Refine the tests since only the secondary side will be invisible with screenshot/icon-view fade animation.

Bug: 278008901
Test: atest WMShellFlickerTests:DragDividerToResize
Change-Id: Idd3f40d0e4da3f55092be9661c61215585d6a68c

libs/WindowManager/Shell/tests/flicker/src/com/android/wm/shell/flicker/CommonAssertions.kt

@@ -223,15 +223,6 @@ fun FlickerTest.splitAppLayerBoundsChanges(
                     portraitPosTop,
                     scenario.endRotation
                 )
-                .then()
-                .isInvisible(component)
-                .then()
-                .splitAppLayerBoundsSnapToDivider(
-                    component,
-                    landscapePosLeft,
-                    portraitPosTop,
-                    scenario.endRotation
-                )
         } else {
             splitAppLayerBoundsSnapToDivider(
                     component,

libs/WindowManager/Shell/tests/flicker/src/com/android/wm/shell/flicker/splitscreen/SplitScreenUtils.kt

@@ -293,7 +293,7 @@ internal object SplitScreenUtils {
             wmHelper.currentState.layerState.displays.firstOrNull { !it.isVirtual }?.layerStackSpace
                 ?: error("Display not found")
         val dividerBar = device.wait(Until.findObject(dividerBarSelector), TIMEOUT_MS)
-        dividerBar.drag(Point(displayBounds.width * 1 / 3, displayBounds.height * 2 / 3), 2000)
+        dividerBar.drag(Point(displayBounds.width * 1 / 3, displayBounds.height * 2 / 3), 200)
 
         wmHelper
             .StateSyncBuilder()