cmd/k8s-operator/deploy/chart,.github/workflows: use helm chart API v2 (#10055)

API v1 is compatible with helm v2 and v2 is not.
However, helm v2 (the Tiller deployment mechanism) was deprecated in 2020
and no-one should be using it anymore.
This PR also adds a CI lint test for helm chart

Updates tailscale/tailscale#9222

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

.github/workflows/kubemanifests.yaml

@@ -0,0 +1,24 @@
+name: "Kubernetes manifests"
+on:
+  pull_request:
+   paths: 
+   - './cmd/k8s-operator/'
+   - '.github/workflows/kubemanifests.yaml'
+
+# Cancel workflow run if there is a newer push to the same PR for which it is
+# running
+concurrency:
+  group: ${{ github.workflow }}-$${{ github.head_ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  testchart:
+    runs-on: [ ubuntu-latest ]
+    steps:
+    - name: Check out code
+      uses: actions/checkout@v4
+    - name: Build and lint Helm chart
+      run: |
+        eval `./tool/go run ./cmd/mkversion`
+        ./tool/helm package --app-version="${VERSION_SHORT}" --version=${VERSION_SHORT} './cmd/k8s-operator/deploy/chart'
+        ./tool/helm lint "tailscale-operator-${VERSION_SHORT}.tgz"

cmd/k8s-operator/deploy/chart/Chart.yaml

@@ -1,7 +1,7 @@
 # Copyright (c) Tailscale Inc & AUTHORS
 # SPDX-License-Identifier: BSD-3-Clause
 
-apiVersion: v1
+apiVersion: v2
 name: tailscale-operator
 description: A Helm chart for Tailscale Kubernetes operator
 home: https://github.com/tailscale/tailscale