By David Lawder WASHINGTON (Reuters) -The U.S. Treasury said on Wednesday it will allow state, local and tribal governments more flexibility to use COVID-19 rescue funds to boost the supply of affordable housing, including permission to issue direct long-term project loans. The changes for the $350 billion State and Local Fiscal Relief Fund program aim to fill a financing gap for affordable housing projects, allowing them to be more easily developed, especially those that are eligible for the Treasury’s Low-Income Housing Tax Credit. “The skyrocketing cost of rent in communities nationwide is …