A few minor changes to standard liftable instances and liftable support

1. Fixes existing `Liftable` definitions to cover more use-cases 
2. Renames `UnliftHelper1` into `UnliftListElementwise` and `UnliftHelper2` into `UnliftListOfListsElementwise`
3. Removes redundant `asInstanceOf` from `Liftable` support implementation

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review @xeno-by