Support FQDN in host field for controlPlaneConfiguration

**What happened**:
Specifying fqdn for `host` under `controlPlaneConfiguration` is currently not supported.

**What you expected to happen**:
`host` name might be misleading as eks-a only actually supports ip right now. Cluster-api also supports fqdn.

**How to reproduce it (as minimally and precisely as possible)**:
Specify fqdn for `host`

**Anything else we need to know?**:
This is a known limitation of eks-a with the intention of adding support to it just like cluster-api does.

**Environment**:
- EKS Anywhere Release:
- EKS Distro Release:

Start from the controlPlaneConfiguration host field and trace how EKS Anywhere validates or consumes it, then compare the expected behavior with the cluster-api support mentioned in the issue. Done means a fully qualified domain name is accepted for host rather than requiring an IP address; the issue does not name specific files or tests.

Written by the indexing model from the issue text.