If the module is enabled (default), 2D physics works as it did before.
If the module is disabled and no other 2D physics server is registered
(via a module or GDExtension), then we fall back to a dummy
implementation which effectively disables 2D physics functionality (and
a warning is printed).
The dummy 2D physics server can also be selected explicitly, in which
case no warning is printed.
Mikael Hermansson
Rémi Verschelde
Ricardo Buring