One of Manhattan’s most prominent builders is poised to take over a West Side assemblage with lucrative development potential. Affiliates of Gary Barnett’s Extell Development and Joe Tabak’s Princeton Real Estate Partners are free to move forward with a credit bid for six adjacent lots along 11th Avenue owned by Robert Gans after he blew a Dec. 22 deadline to settle a $205 million bankruptcy claim, court filings show. Gans, who acknowledged the missed deadline