respect config when setting extendable stores

[martacki]

Changes proposed in this Pull Request

prepare_sector_network currently does not respect the extendable_carrier settings for Stores in the configuration file. If stores are not added as extendable there, the sector coupled model will still add them.

Fix only suggested for battery, depending on decision it could also be extended to H2

While opening that topic, shouldn't the extendable option for techs such as solar rooftop, solar-hsat, etc... also be configurable, rather than assuming that they are?

Checklist

• [x] I tested my contribution locally and it works as intended.
• [x] Code and workflow changes are sufficiently documented.
• [x] Changed dependencies are added to pixi.toml (using pixi add <dependency-name>).
• [x] Changes in configuration options are added in config/config.default.yaml.
• [x] Changes in configuration options are documented in doc/configtables/*.csv.
• [x] Sources of newly added data are documented in doc/data_sources.rst.
• [ ] A release note doc/release_notes.rst is added.