[FEAT] Add jobs to an open batch

[MatthieuMoreau0]

Description

Let users add several jobs at once to a batch. I got rid of the previous function which let users add one job to a batch; but this was very inefficient as it required one http call per job. This is technically a breaking change but it couldn't be used by our users since the dedicated endpoint was always returning an error because batches were automatically marked as complete. Hence I think this can be freely released without worrying about breaking existing pipelines for our users.

Changes:

• Let users create an open batch
• Let users add jobs to an open batch
• Add some documentation on how to create an open batch, add jobs to it and complete it.
• Update changelog
• Update version

Related PRs in other projects (PASQAL developers only)

Additional merge criteria

Breaking changes

Checklist

• The title of the PR follows the right format: [{Label}] {Short Message}. Label examples: IMPROVEMENT, FIX, REFACTORING... Short message is about what your PR changes.

Versioning (PASQAL developers only)

• Update the version of pasqal-cloud in _version.py following the changes in your PR and by using semantic versioning.

Documentation

• Update CHANGELOG.md with a description explaining briefly the changes to the users.

Tests

• Unit tests have been added or adjusted.
• Tests were run locally.

Internal tests pipeline (PASQAL developers only)

• Update and run the internal tests while targeting the branch of this PR.
  If your PR hasn't changed any functionality, it still needs to be validated against internal tests.

After updating the version (PASQAL developers only)

• Open a PR on the internal tests that updates the version used for the pasqal-cloud backward compatibility tests.

[Augustinio]

LGTM, just one question