Move in-process UI creation into a separate DLL.

One step further towards removing widget/GUI dependencies from the core
probe.
Remoting supported is a client/UI property, so move it there.
Extracting a reusable base class of the proxy factory.
Port the ToolFactory proxy to use the new base class.
Add proxy factory for the tool UIs.
We only need the tool UIs here, not the probe part.
All these plugins implement both the probe and the UI interface.
Turn ClientToolModel into a proxy model, usable also in in-process mode.

This will allow us to remove all tool UI related code from the tool model
inside the probe.
Remove tool UI related code from the core tool model.
Completely split ToolFactory and ToolUiFactory.
Fully split built-in tools and their UI.
Don't rely on the core library pulling in the UI library.

That wont be the case much longer, so make the plugins link in that case.
No need to link the probe to the UI library anymore.

There are still several places pulling in QtWidgets though.
Don't link against SVG and print support when using Qt5.
Proxy tool factory is now only used inside the probe, so move it there.
Remove dead code.