WASHINGTON — The Senate will vote Tuesday on bipartisan legislation to protect same-sex and interracial marriages, moving Congress closer to passing the landmark bill and ensuring that such unions are enshrined in federal law.The expected passage of the legislation with support from both parties is an extraordinary sign of the shifting politics on the issue and a measure of relief for the hundreds of thousands of same-sex couples who have married since the Supreme Court’s 2015 Obergefell v. Hodges decision that …