Instance is not updated after a task is ended

### Description of the bug

In scenarious where a task is ended and we are going through the process events, the instance is not updated in database. This can cause errors since the state is incorrect when handling start next task events.

See fix for abandon,
https://github.com/Altinn/app-lib-dotnet/pull/28

### Steps To Reproduce

Will probably cause problems on task where data is not first task and some data should be created

### Additional Information

_No response_

Start by tracing the process-event path for an ended task and compare it with the abandon fix in pull request #28. Reproduce the case where the task is not the first task and verify that the instance state is persisted in the database before the next task's start event is handled.

Written by the indexing model from the issue text.