Handle March 31st + 3 months (June 31st?) for Oracle (#21841)

* Handle March 31st + 3 months for Oracle (#10072)

* Optimize out some casting in Oracle

* rx util support varargs inside `opt`

* hx/ math operators like + and - should propagate type information

* Some dox tweaks

* Fix SQLite busted behavior

* Avoid unneeded casting in Vertica when adding temporal intervals

* Lint error fixes

* BigQuery fix for #21969

* Add testing context for tests for #21968 and #21971