WASHINGTON — The Senate passed bipartisan legislation Tuesday to protect same-sex marriages, an extraordinary sign of shifting national 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 decision that legalized gay marriage nationwide.The bill, which would ensure that same-sex and interracial marriages are enshrined in federal law, was approved 61-36 on Tuesday, including support from 12 Republicans. Senate Majority …