feat: add river-water and sea-water sourced heat pumps

[amos-schledorn]

Closes # (if applicable).

Changes proposed in this Pull Request

This PR adds potential river-water and sea-water sourced heat pumps based on the implementations by @MajaHIC, @juboerms and @felix-land:

• retrieval of HERA data for river discharge and ambient temperature
• retrieval of Copernicus data for seawater temperatures
• Computation of river-water heat potentials per onshore region (approximation of river water temperature from ambient temperature based on Triebs & Tsatsaronis 2022
• Mapping of seawater temperatures to onshore regions
• For both river water and sea water, DEA's excess-heat-sourced heat pumps are assumed for cost data - improvement to be tracked in separate issue

Open TODOs

• Introduce lower temperature threshold for sea water utilisation
• Add Copernicus data to bundle
• Add copyright notice for Copernicus data
• Update data retrieval
• Add plotting procedure for heat potentials
• Final sanity checks

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.