Todd Spangler NY Digital EditorFacebook employees and top execs, including chief operating officer Sheryl Sandberg, were fully aware the social giant was overestimating the projected advertising reach it told marketers — and failed to disclose it to clients for years, according to a newly unsealed legal filing.“Facebook knew for years its Potential Reach [metric] was misleading, and concealed that fact to preserve its own bottom line,” according to the latest filing in the case, released on