Sari the hustler, Duman the gentleman, Bengu the lover, Psikopat the psycho — they may sound like characters straight out of a gangster movie, but they are, in fact, some of the colorful felines profiled in “Kedi,” an endearing documentary about Istanbul’s street cats. For centuries, if not millennia, street cats have roamed the city of Istanbul, where they are not merely tolerated for their rodent-controlling abilities but beloved by its human inhabitants, who feed them and form close attachments to them. Foreign visitors have likewise been captivated by the ubiquitous presence of cats in Turkey’s largest city.