The Islamic Society of Boston's effort to build the region's largest mosque has received at least $1 million in financing from a Saudi Arabia-based bank dominated by governments that critics of the mosque project say support Islamic extremism. The Islamic society acknowledged yesterday receiving a $1 million loan from the Islamic Development Bank in late 2005 -- principal owners of which are Saudi Arabia, Libya, Iran, and Egypt -- after opponents of the mosque project provided the Globe with documents showing that the bank paid about $500,000 in mosque construction bills late in 2005. Work on the mosque, which is...