Add ability to specify whether an operation/path is mapped/imported to 3scale

Current behaviour

The toolbox allows to import an OAS file and will import all defined operations as mapping rules in 3scale.

Expected behaviour

The toolbox can parse the OAS for a 3scale defined extension such as x-map-to-3scale and check a boolean and import or not that path.

Some more context on this is that some API providers don't want to import all paths defined on the OAS so currently they would need to disable those after the fact in each Application Plan.