cmd/k8s-operator: operator can create subnetrouter (#9505)

* k8s-operator,cmd/k8s-operator,Makefile,scripts,.github/workflows: add Connector kube CRD.

Connector CRD allows users to configure the Tailscale Kubernetes operator
to deploy a subnet router to expose cluster CIDRs or
other CIDRs available from within the cluster
to their tailnet.

Also adds various CRD related machinery to
generate CRD YAML, deep copy implementations etc.

Engineers will now have to run
'make kube-generate-all` after changing kube files
to ensure that all generated files are up to date.

* cmd/k8s-operator,k8s-operator: reconcile Connector resources

Reconcile Connector resources, create/delete subnetrouter resources in response to changes to Connector(s).

Connector reconciler will not be started unless
ENABLE_CONNECTOR env var is set to true.
This means that users who don't want to use the alpha
Connector custom resource don't have to install the Connector
CRD to their cluster.
For users who do want to use it the flow is:
- install the CRD
- install the operator (via Helm chart or using static manifests).
For Helm users set .values.enableConnector to true, for static
manifest users, set ENABLE_CONNECTOR to true in the static manifest.

Updates tailscale/tailscale#502


Signed-off-by: Irbe Krumina <irbe@tailscale.com>

.github/workflows/kubemanifests.yaml

@@ -3,6 +3,7 @@ on:
   pull_request:
    paths: 
    - './cmd/k8s-operator/'
+   - './k8s-operator/'
    - '.github/workflows/kubemanifests.yaml'
 
 # Cancel workflow run if there is a newer push to the same PR for which it is
@@ -24,7 +25,7 @@ jobs:
         ./tool/helm lint "tailscale-operator-${VERSION_SHORT}.tgz"
     - name: Verify that static manifests are up to date
       run: |
-        ./tool/go generate tailscale.com/cmd/k8s-operator
+        make kube-generate-all
         echo
         echo
-        git diff --name-only --exit-code || (echo "Static manifests for Tailscale Kubernetes operator are out of date. Please run 'go generate tailscale.com/cmd/k8s-operator' and commit the diff."; exit 1)
+        git diff --name-only --exit-code || (echo "Generated files for Tailscale Kubernetes operator are out of date. Please run 'make kube-generate-all' and commit the diff."; exit 1)