Workload cluster creation errors with capital alphabet in cluster name

**What happened**:
Tried to create a workload cluster with name `workload-cluster-A` on an existing management cluster. EKS-A errored out with logs saying invalid value for cluster metadata.name when applying the config on management cluster.

**What you expected to happen**:
Pre-flights validation should catch this before applying on the management cluster or convert cluster name into small cases before applying on the management cluster.

Provider: CloudStack

Logs:
```
2023-02-14T13:08:19.224-0600 V9 docker {"stderr": "Error from server (Invalid): error when creating \"STDIN\": Cluster.cluster.x-k8s.io \"vgg-cloudstack-A\" is invalid: metadata.name: Invalid value: \"vgg-cloudstack-A\": a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')\nError from server (Invalid): error when creating \"STDIN\": CloudStackCluster.infrastructure.cluster.x-k8s.io \"vgg-cloudstack-A\" is invalid: metadata.name: Invalid value: \"vgg-cloudstack-A\": a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')\nError from server (Invalid): error when creating \"STDIN\": KubeadmControlPlane.controlplane.cluster.x-k8s.io \"vgg-cloudstack-A\" is invalid: metadata.name: Invalid value: \"vgg-cloudstack-A\": a lowercase RFC 1123 subdomain must consist of lower case alphanumeric characters, '-' or '.', and must start and end with an alphanumeric character (e.g. 'example.com', regex used for validation is '[a-z0-9]([-a-z0-9]*[a-z0-9])?(\\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*')
```

Start by locating the workload cluster creation and pre-flight validation paths, then reproduce the issue with a cluster name containing a capital letter. Trace where the name is applied to management-cluster resources and add a regression test covering the invalid name. Done means the invalid name is rejected before application or is consistently converted to a valid lowercase name.

Written by the indexing model from the issue text.