Fix Helm chart enableSecurity flag (#4537)

Fix Helm chart enableSecurity flag:

- Add parameter for whether to use v1alpha cert-manager CRDs, default off.
- Use self-signed Issuer only for the initial CA certificates, create a new
  Issuer that uses the generated CA certificate and use that for all the others

k8s/charts/seaweedfs/values.yaml

@@ -9,6 +9,8 @@ global:
   restartPolicy: Always
   loggingLevel: 1
   enableSecurity: false
+  certificates:
+    alphacrds: false
   monitoring:
     enabled: false
     gatewayHost: null