[HCS-1831] Remove extraneous protocol from fqdn string if present

[aclaygray]

🛠️ Description

This PR updates the logic for generating the k8sAuthMethodHost within the hcp_consul_agent_helm_config data source.

As it stands now we always prepend an https:// protocol to the kubernetes_endpoint string provided. This updated logic will strip a leading https:// from the kubernetes_endpoint string and will leverage the existing logic to prepend the protocol again as needed. This will allow for handling of both cases of this string having a leading https:// and not.

🏗️ Local testing

With the following main.tf

<PROVIDER set-up>

data "hcp_consul_agent_helm_config" "test" {
  cluster_id = "consul-cluster"
  kubernetes_endpoint = "https://catter.com"
}

resulted with the following in terraform.state file:

...
k8sAuthMethodHost: https://catter.com:443
...

The above output is seen with the following main.tf as well:

<PROVIDER set-up>

data "hcp_consul_agent_helm_config" "test" {
  cluster_id = "consul-cluster"
  kubernetes_endpoint = "catter.com"
}

[roaks3]

LGTM