Fix focus in Quick API

The forceActiveFocus() doesn't work in the QML tests.

We need to call forceActiveFocus() in RenderWidgetHostViewQtDelegateQuick
instead of the one in WebEngineView. To make this work, I replaced RWHV
with QQuickWebEngineView in the focus chain.

This is necessary in order to extend tst_loadUrl QML test with
urlProperty test case.

Change-Id: Ifba0c824a7ce9f00d328110233402d3563f967aa
Reviewed-by: Zeno Albisser <zeno.albisser@digia.com>
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>