bugfix: determine bus_carrier locally instead of overwriting n.stores

[lindnemi]

Closes # (if applicable). https://github.com/PyPSA/pypsa-eur/issues/1261

Changes proposed in this Pull Request

Checklist

• [ ] I tested my contribution locally and it seems to work fine.
• [x] Code and workflow changes are sufficiently documented.
• [x] Changed dependencies are added to envs/environment.yaml.
• [x] Changes in configuration options are added in all of config.default.yaml.
• [x] Changes in configuration options are also documented in doc/configtables/*.csv.
• [x] A release note doc/release_notes.rst is added.

[koen-vg]

Thanks for this fix, I've actually had it sitting around locally too but didn't get around to submitting a PR :) Agree that this is the correct approach.

[koen-vg]

CI is failing because a plotting colour is missing for the unsustainable solid biomass carrier; once that's fixed the CI should also work. (I ran into the same issue.)