[energidataservice] Introduce subscription-based providers

[jlaur]

Refactor the binding to use a subscription-based model for better separation of responsibilities and preparing for the future:

• The handler is simplified and stripped of logic for polling data from the service.
• Fetching of electricity prices and CO₂ emissions are extracted into separate providers.
• The cache is rewritten and now has separate implementations for spot prices and tariffs.

Additionally:

• Fix some SAT issues.

Impact of this refactoring:

• Linking new items will no longer cause unnecessary network calls.
• When having multiple Things, they will share the same cache which will reduce network calls and memory consumption.
• Refresh commands will cause all subscribers to be notified if the new data is different from the already cached data.

[lsiepel]

Looks pretty solid. Nice improvement. Just one comment

[lsiepel]

Thanks, LGTM