MI Collection output variable not properly mapped in MI task

[martinweiler]

Add the following assert to the end of IntermediateEventTest.testMultiInstanceLoopCharacteristicsTaskWithOutputCmpCondSequential:

assertThat(((String) instance.variables().getListOut().get(0))).isEqualTo("test");

and the test shows that the variable is not mapped to the collection ouput variable:

expected: "test"
 but was: null

Note: This is also blocking the migration of the testMultiInstanceLoopCharacteristicsTaskWithOutputCompletionCondition2 test as mentioned in apache/incubator-kie-kogito-runtimes#3682