Add wxBitmapBundle::GetPreferredLogicalSizeFor()

We often need the logical bitmap size when using it in size computations
involving window size, so add a function returning it directly to
wxBitmapBundle, similarly to wxBitmap::GetLogicalSize(), to avoid using
FromPhys() everywhere.

Also rename the existing wxBitmapBundle::GetPreferredSizeFor() to
GetPreferredBitmapSizeFor() to make it more clear that this is similar
to wxBitmap::GetSize() and so returns the size in physical units.

Closes #22056.

samples/toolbar/toolbar.cpp

@@ -520,7 +520,7 @@ void MyFrame::PopulateToolbar(wxToolBarBase* toolBar)
                     return m_sizeDef;
                 }
 
-                wxSize GetPreferredSizeAtScale(double scale) const wxOVERRIDE
+                wxSize GetPreferredBitmapSizeAtScale(double scale) const wxOVERRIDE
                 {
                     // We just scale the bitmap to fit the requested size, so
                     // we don't really have any preferences.