add HDPE water pipeline and water booster pump

[doneachh]

Closes # (if applicable).

Changes proposed in this Pull Request

Adding costs for HDPE water pipelines and pumps -> needed for integration of desalination and water management in pypsa-earth

Checklist

• Code changes are sufficiently documented; i.e. new functions contain docstrings and further explanations may be given in doc.
• Data source for new technologies is clearly stated.
• Newly introduced dependencies are added to environment.yaml (if applicable).
• A note for the release notes doc/release_notes.rst of the upcoming release is included.
• I consent to the release of this PR's code under the GPLv3 license.