Add method to load the results of a previous job

[VictorVerhaert]

Add a method to the openeo python client to directly load the result of a previous job. The python client in turn fetches the stac of the previous job and add a load_stac with this link to the PG.

The method should receive either a Job object of a job-id as argument.

[soxofaan]

suggestion: use the method name load_stac_from_job, which is self-explaining and easy to discover (e.g will automatically be suggested by autocomplete functionality if you start typing "load_stac")