Restructure energy storage (function)

[l-emele]

Summary of the discussion

This PR solves large parts of the confusion and inconsistencies of energy storage as function and energy storage as object which was discussed in various issues (#1170, #1174, #1261, #1262 and #1338). This topic was discussed on OEO dev meeting 46. Some parts of this topic are not solved by this PR, but it covers at least the most important part. For the parts that are remaining, we use either existing issues or create new issues.

This is how the energy storage function classes will look like:

And this is how the energy storage object classes will look like:

Type of change (CHANGELOG.md)

Added

• chemical energy storage function
• electrical energy storage function
• kinetic energy storage function
• potential energy storage function
• underground fuel storage object

Updated

• energy storage ➡️ energy storage function
• thermal energy storage ➡️ thermal energy storage function
• energy storage object
• storage unit
• methanation gas storage ➡️ power-to-methane system
• power-to-liquid system
• battery
• pumped water
• pumped hydro storage power plant
• underground hydrogen storage object ➡️ underground hydrogen storage object

Removed

• battery storage
• pumped storage

Workflow checklist

Automation

• Closes #1170
• Closes #1174
• Closes #1262
• Closes #1338

PR-Assignee

• [ ] 🐙 Follow the Pull Request Workflow
• [ ] 📝 Update the CHANGELOG.md
• [ ] 📙 Add #'s to term tracker item

Reviewer

• [ ] 🐙 Follow the Reviewer Guide
• [ ] 🐙 Provided feedback and show sufficient appreciation for the work done

[l-emele]

I just tagged everyone participated in OEO dev meeting 46 as reviewer. :smile:

As this PR touches some core classes of the OEO, I would like to get at least two approvals before I merge.

[l-emele]

Thanks for the review, @lumi321.

As it is a very large PR with more than 100 changed lines, a second review would be good.