DBaas: Simpler K8s registration

Problem: 

Currently, to add K8s into DBaasS, users need to enter two required fields.  This slow's them down.

At the same time, kubeconfig file has information about the cluster name inside and it's often in the buffer already 

User story: 

As a DBaaS Admin, I need to be able to paste kubeconfig from the buffer and also get the suggested cluster name, so my process of adding  k8s cluster is easier.  

UI/UX: 

idea: 

Acceptance criteria

• The user offered a suggestion for k8s Cluster name based on the name in Config 
• user able easily paste file from clipboard 

Out of scope:

• Significant rework of adding k8s
• Support of new technologies
• Discovery
• PMM-10017

Suggested implementation:
TBD

How to test:
TBD

Details:
TBD