* [12.x] Introduce Arr::from()

* Arr::from should not wrap scalar values

* Arr::arrayable helper function

* Arr::from can be used with raw objects except enums; handle UnitEnum instances as scalars

* Add tests

* Replace implicit `getArrayableItems` usage with `Arr::from`

* Handle enums as regular objects in `Arr::from`; wrap enums in `getArrayableItems`

* Remove useless `Arr::arrayable` checks

* Revert to `instanceof Traversable` checks

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Co-authored-by: Sergey Danilchenko <s.danilchenko@ttbooking.ru>