By Trevor Hunnicutt WASHINGTON (Reuters) – President Joe Biden will sign an executive order on Friday pushing federal officials to drive prescription drug costs down during a pre-election trip designed to promote Democrats’ health policies, an official said. The order requires the U.S. Department of Health & Human Services (HHS) to outline within 90 days how it will use new models of care and payment to cut drug costs, according to the White House official, who declined to be identified previewing the president’s action. Biden plans to sign the order during a trip that includes stops in Califo…