cmd/containerboot,kube,ipn/store/kubestore: allow interactive login and empty state Secrets, check perms
* Allow users to pre-create empty state Secrets
* Add a fake internal kube client, test functionality that has dependencies on kube client operations.
* Fix an issue where interactive login was not allowed in an edge case where state Secret does not exist
* Make the CheckSecretPermissions method report whether we have permissions to create/patch a Secret if it's determined that these operations will be needed
Updates tailscale/tailscale#11170
Signed-off-by: Irbe Krumina <irbe@tailscale.com>
Irbe Krumina