The main reason for having the adapters (complex target specific state
handling) is mostly gone now, leaving us mainly with the drawbacks
of the solution: An additional indirection, and using a hierarchy
for code sharing. So drop that, and use if/else chains instead
of virtual functions now, and start simplifying the result.

Change-Id: Idcf3a28da103c01cfa80cf9bab8ef51fe879b6d7
Reviewed-by: Christian Stenger <christian.stenger@qt.io>
Reviewed-by: hjk <hjk@qt.io>