Introduce the component system for managing pre-installed addons

* Previously: Typhoon provisions clusters with kube-system components
like CoreDNS, kube-proxy, and a chosen CNI provider (among flannel,
Calico, or Cilium) pre-installed. This is convenient since clusters
come with "batteries included". But it also means upgrading these
components is generally done in lock-step, by upgrading to a new
Typhoon / Kubernetes release
* It can be valuable to manage these components with a separate
plan/apply process or through automations and deploy systems. For
example, this allows managing CoreDNS separately from the cluster's
lifecycle.
* These "components" will continue to be pre-installed by default,
but a new `components` variable allows them to be disabled and
managed as "addons", components you apply after cluster creation
and manage on a rolling basis. For some of these, we may provide
Terraform modules to aide in managing these components.

```
module "cluster" {
  # defaults
  components = {
    enable = true
    coredns = {
      enable = true
    }
    kube_proxy = {
      enable = true
    }
    # Only the CNI set in var.networking will be installed
    flannel = {
      enable = true
    }
    calico = {
      enable = true
    }
    cilium = {
      enable = true
    }
  }
}
```

An earlier variable `install_container_networking = true/false` has
been removed, since it can now be achieved with this more extensible
and general components mechanism by setting the chosen networking
provider enable field to false.

docs/flatcar-linux/aws.md

@@ -4,7 +4,7 @@ In this tutorial, we'll create a Kubernetes v1.30.1 cluster on AWS with Flatcar
 
 We'll declare a Kubernetes cluster using the Typhoon Terraform module. Then apply the changes to create a VPC, gateway, subnets, security groups, controller instances, worker auto-scaling group, network load balancer, and TLS assets.
 
-Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and `calico` (or `flannel`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
+Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and (`flannel`, `calico`, or `cilium`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
 
 ## Requirements
 

docs/flatcar-linux/azure.md

@@ -4,7 +4,7 @@ In this tutorial, we'll create a Kubernetes v1.30.1 cluster on Azure with Flatca
 
 We'll declare a Kubernetes cluster using the Typhoon Terraform module. Then apply the changes to create a resource group, virtual network, subnets, security groups, controller availability set, worker scale set, load balancer, and TLS assets.
 
-Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and `calico` (or `flannel`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
+Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and (`flannel`, `calico`, or `cilium`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
 
 ## Requirements
 

docs/flatcar-linux/bare-metal.md

@@ -4,7 +4,7 @@ In this tutorial, we'll network boot and provision a Kubernetes v1.30.1 cluster
 
 First, we'll deploy a [Matchbox](https://github.com/poseidon/matchbox) service and setup a network boot environment. Then, we'll declare a Kubernetes cluster using the Typhoon Terraform module and power on machines. On PXE boot, machines will install Container Linux to disk, reboot into the disk install, and provision themselves as Kubernetes controllers or workers via Ignition.
 
-Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns` while `kube-proxy` and `calico` (or `flannel`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
+Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns` while `kube-proxy` and (`flannel`, `calico`, or `cilium`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
 
 ## Requirements
 

docs/flatcar-linux/digitalocean.md

@@ -4,7 +4,7 @@ In this tutorial, we'll create a Kubernetes v1.30.1 cluster on DigitalOcean with
 
 We'll declare a Kubernetes cluster using the Typhoon Terraform module. Then apply the changes to create controller droplets, worker droplets, DNS records, tags, and TLS assets.
 
-Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and `calico` (or `flannel`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
+Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and (`flannel`, `calico`, or `cilium`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
 
 ## Requirements
 

docs/flatcar-linux/google-cloud.md

@@ -4,7 +4,7 @@ In this tutorial, we'll create a Kubernetes v1.30.1 cluster on Google Compute En
 
 We'll declare a Kubernetes cluster using the Typhoon Terraform module. Then apply the changes to create a network, firewall rules, health checks, controller instances, worker managed instance group, load balancers, and TLS assets.
 
-Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and `calico` (or `flannel`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
+Controller hosts are provisioned to run an `etcd-member` peer and a `kubelet` service. Worker hosts run a `kubelet` service. Controller nodes run `kube-apiserver`, `kube-scheduler`, `kube-controller-manager`, and `coredns`, while `kube-proxy` and (`flannel`, `calico`, or `cilium`) run on every node. A generated `kubeconfig` provides `kubectl` access to the cluster.
 
 ## Requirements