Implement BackgroundService and new Actor class

[llucax]

BackgroundService is a new abstract base class can be used to write other classes that runs one or more tasks in the background. It provides a consistent API to start and stop these services and also takes care of the handling of the background tasks. It can also work as an async context manager, giving the service a deterministic lifetime and guaranteed cleanup.

The new Actor class brings quite a few new improvements over the old @actor decorator. These are the main differences:

• It doesn't start automatically, start() needs to be called to start an actor.
• The method to implement the main logic was renamed from run() to _run(), as it is not intended to be run externally.
• Actors can have an optional name (useful for debugging/logging purposes) and loop (if the actor should run in a loop different from the currently running loop).
• The actor will only be restarted if an unhandled Exception is raised by _run(). It will not be restarted if the _run() method finishes normally. If an unhandled BaseException is raised instead, it will be re-raised. For normal cancellation the _run() method should handle asyncio.CancelledError if the cancellation shouldn't be propagated (this is the same as with the decorator).
• The _stop() method is public (stop()) and will cancel() and await for the task to finish, catching the asyncio.CancelledError.
• The join() method is renamed to wait(), but they can also be awaited directly ( await actor).
• For deterministic cleanup, actors can now be used as async context managers.

The base actors (ConfigManagingActor, ComponentMetricsResamplingActor, DataSourcingActor, PowerDistributingActor) now inherit from the new Actor class, as well as the MovingWindow.

Fixes #240, fixes #45, fixes #196.

[Marenz]

In your commit message, insted -> instead, raise -> raised (printed bold in the quoted text)

The main differences with the @actor decorator are:
[...]

• The actor will only be restarted if an unhandled Exception is raise
  by _run(). It will not be restarted if the _run() method finishes
  normally. If an unhandled BaseException is raised insted, it will be

[llucax]

Updated with the suggestions by @Marenz

[Marenz]

Other than those small things, design wise I didn't notice any problems with the code. I would leave a more detailed review once the draft part is over.

[llucax]

OK, now this has all actor classes migrated. I'm pretty happy about the results.

Next step are:

• Remove the actor decorator
• Write tests
• Write release notes
• Update PR description

And in a follow-up PR:

• Migrate other classes to use BackgroundService (like MovingWindow, BatteryPoolStatus, and whatever uses some background tasks and has run/stop/join methods.

[llucax]

Enabling auto-merge

[shsms]

Awesome, everybody get ready to refactor everything now!

[shsms]

Enabling auto-merge

I think you also have to click a button, looks like you just typed the message. :D

[llucax]

It seems like GitHub copilot is not there yet...