Add open submissions to pulser-pasqal

[oliver-gordon]

On the PCS we support open batches, to continuously add new jobs and there is support for this in the SDK but this has not been translated over to pulser-pasqal yet.

Due to the abstraction of batches in this lib I've attempted to keep away the term batch and just flow with open_submission, since our known reference is a submission_id.

When creating a new submission, a user is to either pass the submission_id and we can append new jobs to an existing batch or a boolean flag to indicate whether or not we want the submission being created to be left as open