Fix Kafka topic creation bug due to recent upgrade of AdmissionReview version

[panyuenlau]

Q	A
Bug fix?	yes
New feature?	no
API breaks?	no
Deprecations?	no
License	Apache 2.0

What's in this PR?

• Rename the imported admission pkg name from admissionv1beta1 to admissionv1 so it matches the version with kubebuilder to avoid confusion
• Add Kind and APIVersion to the AdmissionReview since they are required for "admission.k8s.io/v1" requests, reference: https://kubernetes.io/docs/reference/access-authn-authz/extensible-admission-controllers/#webhook-request-and-response

Why?

Kind and APIVersion are not required for "admission.k8s.io/v1beta1" requests but required for "admission.k8s.io/v1", without the necessary fields, the API server rejects the requests with an InternalError, for example:

Error from server (InternalError): error when creating "STDIN": Internal error occurred: failed calling webhook "kafkatopics.kafka.banzaicloud.io": expected webhook response of admission.k8s.io/v1, Kind=AdmissionReview, got /, Kind=

Additional context

In #789 we upgraded the AdmissionReview from v1beta1 to v1, which causes the topic creation to fail. With the fix, kafka topics are created successfully

Checklist

• Implementation tested
• Error handling code meets the guideline
• Logging code meets the guideline
• User guide and development docs updated (if needed)