add constraints for ForeachOp arg

[mhuster23]

fixes #1518

[alexanderpann]

The fix works but in the constraints not only short lambda expressions should be allowed but also lambda expressions.

[mhuster23]

Thanks for the review. The structure only allows ShortLambdaExpression as well, so we can't widen it to lambda expressions without changes to the structure.
If we want to support other Lambda Expressions as well we would need a new common (abstract) superconcept that extends Expression and implements ILambdaLike. As we can't use ILambdaLike for the link as it is not a subconcept of OneArgCollectionOp.
I'm not sure if we want this.

[alexanderpann]

Right, but then the intention transformIntoExplicitVersion has to be fixed. It currently allows changing the lambda for the ForeachOP to a lambda expression.

[mhuster23]

I didn't like that forEach was treated differently than other operations. So I tried a different approach, that unifies the behavior but also affects other operations that use lambdas.

Removing the arg specialization does not break models but it will break usages of the link, however this is probably fine because the name is the same so a refresh will re-resolve usages.

[alexanderpann]

LGTM. I guess the breaking of the link can't be avoided.