API/UI: Support custom-constrained and custom-unconstrained offerings when creating a CKS cluster

### problem

Currently, users are unable to select the custom-constrained and custom-unconstrained offerings from the UI

And also it's not even possible from the API as we are excluding the custom offerings for cks cluster

```
localcloud) 🐱 > create kubernetescluster name=test zoneid=fb0bd189-c018-4897-8a2d-7f9b59b204da hypervisor=KVM kubernetesversionid=515fb765-38f3-4ca1-bd6d-18816b64418b serviceofferingid=7ebfd3b9-1b0e-44ca-b9ec-4ebeff9df06e size=1

🙈 Error: (HTTP 530, error code 9999) Given service offering ID: Service offering {"id":13,"name":"Large Instance-unconstrained","uuid":"7ebfd3b9-1b0e-44ca-b9ec-4ebeff9df06e"}. for WORKER nodes is not suitable for the Kubernetes cluster version KubernetesSupportedVersion {"id":1,"name":"cks-csi","semanticVersion":"1.33.1","uuid":"515fb765-38f3-4ca1-bd6d-18816b64418b"} - Custom service offerings are not supported for creating clusters, service offering ID: 7ebfd3b9-1b0e-44ca-b9ec-4ebeff9df06e

(localcloud) 🐱 > create kubernetescluster name=test zoneid=fb0bd189-c018-4897-8a2d-7f9b59b204da hypervisor=KVM kubernetesversionid=515fb765-38f3-4ca1-bd6d-18816b64418b
serviceofferingid=bdf374a9-c55b-46dc-b5c1-c8056beb8d10 size=1

🙈 Error: (HTTP 530, error code 9999) Given service offering ID: Service offering {"id":14,"name":"Large-Instance-constrained","uuid":"bdf374a9-c55b-46dc-b5c1-c8056beb8d10"}. for WORKER nodes is not suitable for the Kubernetes cluster version KubernetesSupportedVersion {"id":1,"name":"cks-csi","semanticVersion":"1.33.1","uuid":"515fb765-38f3-4ca1-bd6d-18816b64418b"} - Custom service offerings are not supported for creating clusters, service offering ID: bdf374a9-c55b-46dc-b5c1-c8056beb8d10

```

### versions

ACS 4.21, 4.20.1

### The steps to reproduce the bug

1. Navigate to service offering > compute offering > create a custom-constrained and custom-unconstrained offering.

Create a custom -constrained offering od 2 cpu and 2048 ram which is the minimum requirement for a cks cluster

2. Navigate to compute > kubernetes > create cks cluster

3. The custom-constrained and custom-unconstrained are listed

...

### What to do about it?

User should be able to select the custom-constrained and custom-unconstrained offerings for a cks cluster.

As it would be beneficial for the end user to specify the CPU and memory during CKS creation

A similar box related to deploy instance should be displayed during cks creation

Commencez par suivre la création de clusters CKS via l’API et l’UI, en vous concentrant sur l’endroit où les offres de service custom-constrained et custom-unconstrained sont exclues. Reproduisez le problème avec les offres personnalisées décrites dans le rapport ; le travail est terminé lorsque les deux offres peuvent être sélectionnées dans le flux de création de CKS et acceptées par l’API.

Rédigé par le modèle d'indexation à partir du texte de l'issue.