Split controllers and webhooks into separate packages

[danail-branekov]

Is there a related GitHub Issue?

#3304

What is this change about?

Having controllers in separate packages allows having a suite per a
controller. This has several benefits:

• The suite setup is significantly simpler - it does not have to wire
  all the controllers/webhooks. Instead, the setup wires only the
  controller/webhook that is being tested
• Not wiring all the controllers in the test env reduces the noise of
  unrelated controllers/webhooks. This allows tests to not care about
  creating "valid" dependent objects, they only create dependent
  objects with properties that are just relevant to the
  controller/webhook under test
• Tests are no longer required to take side effects from neighbour
  controllers/webhooks into consideration
• Instead of relying on a state change of a dependent object caused by a
  neightbour controller, the test could simply set the desired state of
  the dependent object. This makes the test simpler and easy to reason
  about

This change follows several patterns:

1. Move existing controllers and webhooks and their tests into separatepackages
2. Come up with a minimal testenv suite that makes the tests happy
3. Rename controller types by removing their type prefix (as it is contained in the package already). For example, CFAppReconciler is renamed to just Reconciler
4. Related file names have their resource name removed, for example cfapp_controller.go is renamed to controller.go

In the process of the refactoring above, tests are refactored:

• Overall simplification
• Prefer creating literals with the data only needed by the test vs using an utility function that creates a monster object with lots of unnecessary data

Does this PR introduce a breaking change?

No

Acceptance Steps

tests passing

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@cloudfoundry/wg-cf-on-k8s