Start using next step ids (#11683)

- update workflow executor
- update next step ids on step creation/deletion
- use these in workflow run
- use these in variables

packages/twenty-server/src/engine/core-modules/workflow/dtos/workflow-step.dto.ts

@@ -21,4 +21,7 @@ export class WorkflowActionDTO {
 
   @Field(() => Boolean)
   valid: boolean;
+
+  @Field(() => [UUIDScalarType], { nullable: true })
+  nextStepIds?: string[];
 }