MaxScale should warn about inconsistencies in the configuration file

If there are sections in the configuration file that are not used, MaxScale should at startup log a warning about them. E.g. something like:

2023-11-02 10:42:18   warning : Section 'cache-default' in /etc/maxscale.cnf is defined but not used.

That way simple mistakes such as creating a filter without associating it with a service would be caught.