Implement platform-specific coordinate conversion functions

Generic wxDC::DeviceToLogical{X|Y}() and wxDC::LogicalToDevice{X|Y}()
functions don't take into account transformations applied with
wxDC::SetTransformMatrix() so conversion results are invalid if wxDC is
transformed with both e.g. wxDC::SetUserScale() and
wxDC::SetTransformMatrix().
We need to implement functions in wxDCImpl and its platform-specific
derivates to do this conversion with taking into account all applied
transformations.

See #18916.

include/wx/dc.h

@@ -323,6 +323,10 @@ public:
     // flushing the content of this dc immediately eg onto screen
     virtual void Flush() { }
 
+    // coordinates conversions and transforms
+    virtual wxPoint DeviceToLogical(wxCoord x, wxCoord y) const;
+    virtual wxPoint LogicalToDevice(wxCoord x, wxCoord y) const;
+
     // bounding box
 
     virtual void CalcBoundingBox(wxCoord x, wxCoord y)