By Emma Farge and Olivia Le Poidevin GENEVA, Jan ?23 (Reuters) - ?The U.N. Human Rights Council ?will hold an emergency session on Friday to discuss the "alarming violence" ?used in Iran against protesters, while a group of states will call on United Nations' investigators to ?document alleged abuses for future ?trials. Rights groups say thousands, including bystanders, were killed during the unrest, which represented the ?biggest challenge ?to Iran's clerical government since 2022. At least 50 countries backed the call for a special session of the U.N. Human Rights Council to address credible reports of violence, crackdowns on protesters...