feat(sqlite): Support stdlib functions (#1712)

* move existing builtins to postgresql folder

* [sqlite] support built-in aggregate functions

https://www.sqlite.org/lang_aggfunc.html

* [sqlite] support built-in mathematical functions

https://www.sqlite.org/lang_mathfunc.html

* [sqlite] support built-in scalar functions

https://www.sqlite.org/lang_corefunc.html

Author: hakobera

internal/endtoend/testdata/builtins/go/db.go renamed to internal/endtoend/testdata/builtins/postgresql/go/db.go

@@ -8,4 +8,4 @@
       "queries": "query.sql"
     }
   ]
-}
+}