Several restaurants and more than a dozen retail shops could open at Providence’s renovated Arcade mall as early as next month. The Providence Journal reported that building owner Evan Granoff says four restaurants and 14 small retailers could occupy the first floor of the historic Westminster Street building by the end of September. As part of the $7 million renovation project, the top two floors will be turned into 48 residential ‘‘microlofts’’ up to 450 square feet. No leases have been signed on those spaces yet. The Arcade was built in 1828 and is the nation’s oldest indoor shopping mall. It is on the National Register of Historic Places. It has been closed since 2008.