DMN16 — Filter and Iterator in attribute should not require a collection

Currently the in parameter is defined as: This attribute holds the expression that is evaluated as the collection to be processed.

The intention was to align with the FEEL version of filter and iterators and therefore apply the the 10.3.2.9.4 Type conversions rule: to singleton list: When the type of the expression is T and the target type is List<T> the expression is converted to a singleton list.

The definition of the in parameter needs to be updated to properly reflect this.