[v1.6] Bump Go to 1.22 and RKE to 1.6.2

[jiaqiluo]

https://github.com/rancher/terraform-provider-rke/issues/460

This PR includes the following updates:

• Upgraded Go to version 1.22 and RKE to version 1.6.2
• Removed usage of the deprecated ioutil package from the standard library
• Updated the README file

Testing

Since there is no CI available to run tests on the PR, all tests are executed locally using make test.

The basic functionality has also been verified.

Below is the Terraform configuration file used to create a one-node RKE cluster with all roles. Note that Terraform is configured to use the binary built from the PR:

# main.tf

terraform {
  required_providers {
    rke = {
      source = "rancher/rke"
      version = "1.4.4"
    }
  }
}

# Configure the RKE provider
provider "rke" {
  debug = true
  log_file = "./logfile.txt"
}
resource rke_cluster "cluster" {
  enable_cri_dockerd = "true"
  kubernetes_version = "v1.30.4-rancher1-1"
  nodes {
    address = "x.xx.x.x"
    internal_address = "x.xx.x.x"
    user    = "root"
    role    = ["controlplane", "etcd", "worker"]
  }

resource "local_file" "kube_cluster_yaml" {
  filename = "${path.root}/kube_config_cluster.yml"
  content  = rke_cluster.cluster.kube_config_yaml
}