Previous PR[1] which deprecated `thanosSelector` accidentally broke the usage of it. This commit restores the old behaviour along with newly introduced `thanos` config variable. [1] https://github.com/prometheus-operator/kube-prometheus/pull/1543 Co-authored-by: Pawe? Krupa <pawel@krupa.net.pl> Signed-off-by: Arunprasad Rajkumar <arajkuma@redhat.com>