Android: call requestApplyInsets() after system ui visibility change

Always call decorView.requestApplyInsets() after a system ui
visibility change. This ensures the insets are updated and we
don't end up with wrong window sizes or half-way transitions
to different visibility states. With this change, the various
transitions are no longer flaky, many tests for safe margins
and fullscreen dimensions under tst_android are now reliably
executed over multiple iterations.

Pick-to: 6.10 6.10.0 6.9 6.8
Change-Id: I69260f76aa0a0e67f65918b6a8b10413cae13fd4
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

src/android/jar/src/org/qtproject/qt/android/QtDisplayManager.java

@@ -214,6 +214,8 @@ class QtDisplayManager
                 window.setNavigationBarColor(defaultNavigationBarColor);
             }
         }
+
+        decorView.post(() -> decorView.requestApplyInsets());
     }
 
     boolean isFullScreen()