Simple core and layered reconciler implementation for v6

現在の Reconciler と ReconciliationDispatcher の責務（updateErrorStatus を含む）を確認し、その後、提案されている GenericReconciler 層と WorkflowReconciler 層のプロトタイプを作成してください。完了条件は、動作するプロトタイプと、核心となる分離を説明し、既存ユーザーの移行を簡単なままにする適切な設計説明があることです。

TL;DR We could make the core of the framework simpler by introducing a more layered architecture. While keeping the migration for the users trivial.

Problem definition

Currently the core of a framework has baked logic to work with higher level logic like:

• Adding finalizers by implementing Cleaner interface
• Managed workflows inside the controller
• Automatic generation filtering
• Catching error and error handling, thus updateErrorStatus method.

We recently added a generic mode Trigger reconciliation on all events

While it makes a nice API for the users, an maybe even nice out of the box experience, makes the core of the framework more complex - and even for users I assume hard to follow, if some wants to read the code.

What we could do in next major version is to layer those functionalities:

1. The core will just work on top of a simplified Reconciler interface. What will handle basically be the all event mode. So we won't support finalizers, UpdateControl.patch methods ,and most of the functionality of ReconciliationDispatcher would be moved to an abstract Reconciler implementation: GenericReconciler.
2. Retry, Rate limiting would stay as it is now
3. The managed workflow handling would an additional extension of GenericReconciler: WorkflowReconciler. That will handle the managed workflow discovery, their configuration etc.

Migration

Note that migration for the users could be kept trivial, basically just extending the GenericReconciler / WorkflowReconciler (Where we could support the UpdateControl etc as is now) instead of implementing Reconciler.

Pros

• The core would be much simpler
• The logic around these extended reconcilers much easier to be followed by the users (from source code)

Cons

• This does not provide direct value for users, other than easier to handle

Notes

• before we make a decision, we should explore this first in a proptotype
• TODO: proper design description