Breaking change 56065: Change the context for the operand of throw to Object.

[Paul Berry]

The type schema for type inference of the operand of a throw expression will be changed from _ (the unknown type) to non-nullable Object.

This change is expected to have very low impact on real-world code. But in principle it could cause changes in runtime behavior.

For additional details please see https://github.com/dart-lang/sdk/issues/56065.

If this breaking change poses a severe problem, please leave comments in the linked issue.