Remove redundant touch processing in QtGui and widgets.

Remove redundant touch processing in QtGui and widgets.

The duplicated hash tables in QGuiApplicationPrivate and
QApplicationPrivate are now unified into one single hash table in
QGuiApplicationPrivate. This also reduced the number of lookups.

The extra processing needed to keep the touch points' first/lastPos
values in sync is now done only once, in QGuiApplication. This
eliminates the performance penalty (for widget-based apps) that was
introduced during the QPA migration.

As an added bonus the patch adds support for touch events arriving
simultaenously from multiple devices. This was broken before: As there
is no guarantee that two devices/drivers will not send touch points
with the same ID, using structures with only the ID as key is
wrong. The proper key is composed of the device ID (that is, a
QTouchDevice pointer) and the touch point ID.

The exported internal function qt_translateRawTouchEvent() has been
removed. This function cannot work properly in the QPA world: It
injected touches into the widget subsystem (QApplication) only which
is wrong, and would result in half-filled touch events due to not
routing the injected data through QGuiApplication. Autotests using
this function are migrated to
QWindowSystemInterface::handleTouchEvent().

Change-Id: I7632781d77f9e0ac4626fd7c9933511c94492156
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>