LONDON/MADRID (Reuters) - Dozens of ships carrying liquefied natural gas (LNG) circling off the coasts of Spain unable to secure slots to unload have prompted grid operators for the country to warn they may have to suspend loading to deal with this "exceptional situation". Europe is facing an energy supply squeeze as Russia has progressively cut gas flows after the West imposed sanctions in response to Russia's invasion of Ukraine in late February. The region has had to find alternative supplies, including LNG, but the arrival of multiple cargoes of the superchilled fuel has exposed Europe's lack of "regasification" capacity,...