feat(@angular/cdk/cdkDrag): cdkDragEnded out of a container

[bbogdanov]

Bug, feature request, or proposal:

Having a property in cdkDragEnded event that indicates the user item drag ended out a container.

For example:
outOfContainer: boolean = false;

What is the expected behavior?

The cdkDragEnded on emit to have an infromation about the user dropping the item out of a container.

What is the current behavior?

There is no such behavior at the moment.

What is the use-case or motivation for changing an existing behavior?

I think is a good information to know an the item was dropped out of a container.

Which versions of Angular, Material, OS, TypeScript, browsers are affected?

7+

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