Add epoch funcs for BigQuery (#7567)
Add epoch funcs for BigQuery (#7567)


airbnb/caravel,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,mistercrunch/panoramix,mistercrunch/panoramix,apache/incubator-superset,mistercrunch/panoramix,airbnb/superset,zhouyao1994/incubator-superset,apache/incubator-superset,airbnb/caravel,airbnb/superset,mistercrunch/panoramix,airbnb/superset,airbnb/caravel,apache/incubator-superset,airbnb/caravel,apache/incubator-superset,apache/incubator-superset,airbnb/superset