Restructuring config for carrier networks

[bobbyxng]

Closes # (if applicable).

Changes proposed in this Pull Request

• Propose to clean up and structure config wrt. networks (CO2, H2, gas, biomass, etc...)
• Allowing finer control of p_nom max, extendable policies, inclusion of planned projects (PCI/PMI, EHB, to be implemented)
• This thread serves as a platform for discussion first

Checklist

• [ ] I tested my contribution locally and it works as intended.
• [ ] Code and workflow changes are sufficiently documented.
• [ ] Changed dependencies are added to envs/environment.yaml.
• [ ] Changes in configuration options are added in config/config.default.yaml.
• [ ] Changes in configuration options are documented in doc/configtables/*.csv.
• [ ] Sources of newly added data are documented in doc/data_sources.rst.
• [ ] A release note doc/release_notes.rst is added.

[fneum]

For any config restructuring, we need #1547 first.