Land transport fix

[lisazeyen]

Changes proposed in this Pull Request

This PR converts all land transport demand to one single node and adds the different land transport options (EV, fuel cell, internal combustion car) as links.

This is a bug fix since currently efficiency are adjusted with the assumptions that all cars would be EVs (what is not the case for myopic optimisation) and is a preparation for endogenousing the land transport.

Checklist

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

[lisazeyen]

just a ping for @fneum or maybe @p-glaum can have a look?