[Deletion Modes] Implement logic for "unmanaging" a Module

Description

There should be an option to unmanage a module. When unmanaged, the KLM deletes the module's ManifestCR and stops reconciling the module. However, the workload (module resources deployed to the SKR) is not affected.

Reasons

In some cases, users would like to have full control over their Modules' lifecycle.

Acceptance Criteria

[x] When the user sets .spec.modules[].managed: false
- [x] KLM deletes module's ManifestCR without affecting deployed resources
- [x] module's workload (resources deployed to the SKR) remain to exist
- [x] KLM does NOT reconcile the module's workload any longer
- [x] KLM sets KymaCR .status.state and .status.modules[] to
```
status:
state: Ready
modules:
- name: some-module
state: Unmanaged
```
[x] When the KymaCR is:
```
spec:
  modules:
  - name: some-module
    managed: false
status:
  state: Ready
  modules:
  - name: some-module
    state: Unmanaged
```
And the user removes the module completely from spec.modules[]
- [x] KLM deletes module from KymaCR .status.modules[]
- [x] module's workload (resources deployed to the SKR) remain to exist
- [x] KLM does NOT reconcile the module's workload
- [x] KLM sets KymaCR .status.state to Ready
[x] Documentation clearly states that
- [x] Before removing an entry from .spec.modules[] that has managed: false set, the related .status.modules[].state MUST be Unmanaged
- [x] If the entry is removed before .status.modules[].state transitioned to Unmanaged, the behavior of the deletion is unpredictable (i.e., either behaves like deletion of a managed or unmanaged module) and may lead to erroneous states

Feature Testing

End-to-End tests

Testing approach

E2E Test:

Given a Kyma Module with managed set to true
- And a SKR Kyma CR is created on the SKR Cluster
- And a Manifest CR is created on the KCP Cluster
- And - Module Operator, Module CR, and [Module Managed Resources] are created on the SKR Cluster
- And Kyma Status is in a Ready State
When the Managed field is set to false for the Kyma Module
- Then the Kyma Module is no longer reconciled
  - Module Status for that Kyma Module becomes Unmanaged
  - Manifest CR is removed from the KCP Cluster
  - Module Operator, Module CR, and [Module Managed Resources] are kept intact in the SKR Cluster
  - And Kyma Status is in a Ready State
When Kyma Module is removed from kyma.spec.modules list
- Then Module Operator, Module CR, and [Module Managed Resources] are kept intact in the SKR Cluster
- And Kyma Status is in a Ready State
- And Module Status for that Kyma Module is deleted

Attachments

No response

kyma-project / lifecycle-manager

[Deletion Modes] Implement logic for "unmanaging" a Module #1427