Accordion tree use in Services

* use `accordion.tree` instead of relying on custom locators.
* some refactoring.
    * import ordering.
    * tried to normalize some variable names to the common ones.
    * I tried to make the trees a bit more readable.

`test_generic_service_catalogs` gave me 100% pass, others still fail but not on nav issues or so.

Will probably also need #850 to get the best pass rate.