fix: Update time grain expressions for Spark >= 3.x (#18690)
fix: Update time grain expressions for Spark >= 3.x (#18690)

* Fix the time grain expressions for Spark >= 2.3.0

Spark removed date format string 'u' in Spark 3.0. Switch to using date_trunc which has been around since 2.3

* Review: Pull out time_grain_expressoins into its own thing
zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,airbnb/caravel,airbnb/caravel,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,zhouyao1994/incubator-superset,airbnb/caravel,airbnb/caravel