G.A-T and D.R-G are partially supported by the Spanish government grant MINECO16-FPA2015-63667-P. They also acknowledge support from the Principado de Asturias through the grant FC-GRUPIN-IDI/2018/000174. The work of A.B. is supported by STFC grant ST/P000762/1 and grant EP/K034456/1. A.P. is supported by the German Research Foundation (DFG) via the Emmy Noether program “Exact results in Gauge theories”.