Add API for regulating if a specific event type should be compressed.

In Qt4 there was a widget attribute for disabling motion event compression WA_NoX11EventCompression. This attribute is X11 specific thus only one of the supported platforms had this feature available.

There are use cases when event compression is not desirable, a quote from GTK+ docs:

Some types of applications, e.g. paint programs, need to see all motion events and will benefit from turning off event compression. [1]

Currently in Qt5 if you want to get uncompressed (all) events then you would need to use QAbstractNativeEventFilter. This is not very cross-platform, because you have to deal with native event types. The solution would be to add flags that could be used to disable compression for specific event types (only those that make sense), for example:

DontCompressMotion,
DontCompressTouch,
DontCompressAll

The question are:

• do we want to disable this for selected windows or for the whole QPA plugin?
• where the actual compression should take a place (it needs to work in both - in widget code and in qtquick code)?

[1] https://developer.gnome.org/gdk3/stable/gdk3-Windows.html#gdk-window-set-event-compression