NEW YORK — Dwayne Montgomery, a former NYPD inspector and longtime friend of Mayor Eric Adams, admitted as part of a guilty plea Monday that he helped orchestrate a scheme to funnel illegal donations into the mayor’s 2021 campaign coffers. During a morning hearing in Manhattan Criminal Court, Montgomery copped to one count of fifth-degree conspiracy, a Class A misdemeanor, a spokeswoman for District Attorney Alvin Bragg confirmed. Under his plea deal, Montgomery is admitting he conspired with construction contractor Shamsuddin Riza and five other men between at least August 2020 and November 2…