Add "fullnameOverride" support to Helm chart

The attribute "fullnameOverride" by default, allows you to adjust how the resources part of the Helm chart are named.

This allows the engineer consuming the Helm chart to determine how pods and services are named in the Kubernetes cluster.

This is even supported by default as can be observed in https://github.com/helm/helm/blob/main/pkg/chartutil/create.go#L474-L485

Allowing this would allow the pods to be named, instead of:

couchbase-operator-admission-controller-6d98865c58-75hk8   1/1     Running   0          70m
couchbase-operator-couchbase-operator-77fc5dbbb8-jfsl6     1/1     Running   0          77m

To be named:

couchbase-admission-controller-6d98865c58-75hk8   1/1     Running   0          70m
couchbase-operator-77fc5dbbb8-jfsl6               1/1     Running   0          77m

With the following values.yaml:

```yaml
couchbaseOperator:
  fullnameOverride: couchbase-operator
admissionController:
  fullnameOverride: couchbase-admission-controller
```