[Meta] Migrate Libbeat plugins to the Global registry

[ph]

With the introduction of #7392 we can refactor plugins to use the new registry instead of a custom registry for each plugin type.

• Autodiscover
  • Provider
  • builder
  • appenders
• Processor Migrate processor to the new global registry #7396
• Queue
• Output Feature/migrate outputs to the new registry #7400
• Codec (output codec)
• Refactor go-plugins to use the new Feature instead of the old Plugin.
• Update Filebeat to the new plugin concept.
• Update Filebeat code generator with the new concept
• Beat developer: How to discover features, can we generate a list automatically and add it to the doc.
• Pass feature.Details instead of stability only this would make us a bit more feature proof.

[exekias]

@urso is this one still relevant?

[urso]

Yes, it's still relevant. We might still need to evaulate if the solution in #7392 is good enough, but some ideas in it are definitely an improvement.

[jlind23]

Backlog grooming: Closing it for now until further activity, can still be reopened if needed.