rename networkclustering namespace

[pz-max]

Closes #784

Allows pypsa>=0.23, <0.25 ... opened a new issue for using pypsa>=0.25

Checklist

• I consent to the release of this PR's code under the AGPLv3 license and non-code contributions under CC0-1.0 and CC-BY-4.0.
• I tested my contribution locally and it seems to work fine.
• Code and workflow changes are sufficiently documented.
• Newly introduced dependencies are added to envs/environment.yaml and doc/requirements.txt.
• Changes in configuration options are added in all of config.default.yaml and config.tutorial.yaml.
• Add a test config or line additions to test/ (note tests are changing the config.tutorial.yaml)
• Changes in configuration options are also documented in doc/configtables/*.csv and line references are adjusted in doc/configuration.rst and doc/tutorial.rst.
• A note for the release notes doc/release_notes.rst is amended in the format of previous release notes, including reference to the requested PR.

[pz-max]

To allow in the env.yaml pypsa>=0.25 we need to upgrade the network clustering: PyPSA/pypsa-eur#696 (at the time of writing in a PR in PyPSA-Eur)