Replace Dryrun and Rerun logick in InstancesController.

### Description

When we create new instances today we first do a dryrun of starting the process and moving it to the first task.
After this has succeeded we create the instance already at the first task in the process, then we rerun all the events related to the dryrun.

### Additional Information

_No response_

Start by locating InstancesController and tracing the instance-creation flow described in the issue, including the dryrun, first-task transition, and event rerun. The issue does not identify tests or define the replacement behavior; done would require an agreed design that removes or changes this sequence.

Written by the indexing model from the issue text.