DATE test: hold Result.to_json() to the form the loaded engine uses #339

Review of ArcadeData#10312 (CodeRabbit): test_to_json_list_writes_a_date_as_midnight_utc_in_any_jvm_zone accepts either form from Result.to_json() (midnight UTC milliseconds or days since the epoch), so an engine that went back to milliseconds after ArcadeData#10253 would still pass.

Ask the engine which form it uses, Type.getTypeByValue(LocalDate) (DATE since ArcadeData#10253, null before), and hold to_json() to that one value. A version check cannot do it: 26.11.1 snapshots from before ArcadeData#10253 exist.