Validate that any tags that users have specified via tailscale.com/tags
annotation are valid Tailscale ACL tags.
Validate that no more than one HA Tailscale Kubernetes Services in a single cluster refer
to the same Tailscale Service.
Updates tailscale/tailscale#16054
Updates tailscale/tailscale#16035
Signed-off-by: Irbe Krumina <irbe@tailscale.com>