Return wxWindow* from wxDataViewCustomRenderer::CreateEditorCtrl().

There's no reason to limit custom editor controls to wxControl, which
would rule out e.g. composite controls or any custom widgets.
Make appropriate changes to related functions and code too.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@67576 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775