By Carmel Crimmins and Sinead Cruise DUBLIN/LONDON (Reuters) - Though the implosion of Cyprus's bloated banking system has put other euro zone economies with outsized financial sectors such as Luxembourg and Malta in the spotlight, loan quality is the real litmus test of a country's financial stability. Attracted by low taxes, high interest rates and light regulation, foreign deposits, largely from Russia and other former Soviet states, pumped up the Cypriot banking sector to nearly eight times annual economic output, more than double the European average of around 3.5 times. ...