[macOS] Fix FlutterView cursor hit testing (flutter#53171)

fix cursor hit testing in platform view in flutter#52159

We found that the mechanism of `[NSView hitTest: view] `will handle the
flip coordinate automatically. In the previous PR, because the superview
of FlutterView was not flipped, we should not convert the point using
`[self convertPoint:event.locationInWindow fromView:nil]` .The
FlutterView hit test should run under the window coordinate system;
otherwise, FlutterMutatorView will hit a wrong point.

Before the fix:
Actual mouse move: `event.locationInWindow (x = 47.45703125, y =
416.86328125)`
FlutterView HitTest: `(NSPoint) point = (x = 47.45703125, y =
203.13671875)`
FlutterMutatorView HitTest: `(NSPoint) point = (x = 47.45703125, y =
416.86328125)`

After the fix:
Actual mouse move: `event.locationInWindow (x = 47.45703125, y =
416.86328125)`
FlutterView HitTest: `(NSPoint) point = (x = 47.45703125, y =
416.86328125)`
FlutterMutatorView HitTest: `(NSPoint) point = (x = 47.45703125, y =
203.13671875)`


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shell/platform/darwin/macos/framework/Source/FlutterView.mm

@@ -107,7 +107,8 @@ - (void)didUpdateMouseCursor:(NSCursor*)cursor {
 // and will not restore it back.
 - (void)cursorUpdate:(NSEvent*)event {
   // Make sure to not override cursor when over a platform view.
-  NSView* hitTestView = [self hitTest:[self convertPoint:event.locationInWindow fromView:nil]];
+  NSPoint mouseLocation = [[self superview] convertPoint:event.locationInWindow fromView:nil];
+  NSView* hitTestView = [self hitTest:mouseLocation];
   if (hitTestView != self) {
     return;
   }

shell/platform/darwin/macos/framework/Source/FlutterViewTest.mm

@@ -110,7 +110,7 @@ - (void)set {
 
   EXPECT_TRUE(hitTestCalled);
   // The hit test coordinate should be in the window coordinate system.
-  EXPECT_TRUE(CGPointEqualToPoint(hitTestCoordinate, CGPointMake(100, 500)));
+  EXPECT_TRUE(CGPointEqualToPoint(hitTestCoordinate, CGPointMake(100, 100)));
   EXPECT_TRUE(cursor.setCalled);
 }
 
@@ -155,6 +155,6 @@ - (void)set {
 
   EXPECT_TRUE(hitTestCalled);
   // The hit test coordinate should be in the window coordinate system.
-  EXPECT_TRUE(CGPointEqualToPoint(hitTestCoordinate, CGPointMake(100, 500)));
+  EXPECT_TRUE(CGPointEqualToPoint(hitTestCoordinate, CGPointMake(100, 100)));
   EXPECT_FALSE(cursor.setCalled);
 }