Fix TextInput and TextEdit inputMethodComposing autotests

Fix TextInput and TextEdit inputMethodComposing autotests

In old QInputContext architecture events were send to focus
widget, which delivered the events to the text editor items.
In Qt5, input methods send events directly to the editor
object using QInputPanel::inputItem().

Task-number: QTBUG-21691

Change-Id: Ia219f0cc7caaeafc32f5d7674a6ab377e773d4fa
Reviewed-on: http://codereview.qt-project.org/5741
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Andrew den Exter <andrew.den-exter@nokia.com>
Reviewed-by: Lars Knoll <lars.knoll@nokia.com>