Allow CoreDNS and kube-proxy to be optional components

* Allow for more minimal base cluster setups, that manage CoreDNS or
kube-proxy as applications, with rolling updates, or deploy systems.
Or in the case of kube-proxy, its becoming more common to not install
it and instead use Cilium
* Add a `components` pass-through variable to configure pre-installed
components like kube-proxy and CoreDNS. These components can be
disabled (individually or together) to allow for managing components
with separate plan/apply processes or automations
* terraform-render-bootstrap manifest assets are now structured as
manifests/{coredns,kube-proxy,network} so adapt the controller
layout scripts accordingly
* This is similar to some changes in v1.29.2 that allowed for the
container networking provider manifests to be skipped

Related: https://github.com/poseidon/typhoon/pull/1419, https://github.com/poseidon/typhoon/pull/1421

google-cloud/flatcar-linux/kubernetes/variables.tf

@@ -147,3 +147,16 @@ variable "daemonset_tolerations" {
   description = "List of additional taint keys kube-system DaemonSets should tolerate (e.g. ['custom-role', 'gpu-role'])"
   default     = []
 }
+
+variable "components" {
+  description = "Configure pre-installed cluster components"
+  # Component configs are passed through to terraform-render-bootstrap,
+  # which handles type enforcement and defines defaults
+  # https://github.com/poseidon/terraform-render-bootstrap/blob/main/variables.tf#L95
+  type = object({
+    enable     = optional(bool)
+    coredns    = optional(map(any))
+    kube_proxy = optional(map(any))
+  })
+  default = null
+}