chore(orchestration): prevent throwing on already defined workflow (#5337)

**What**
At the moment, when importing something from medusa entry point, if two medusa packages are installed because of a plugin, the evaluation of the import can end up throwing that a workflow is already defined. To prevent that from happening, we can just not throw if it is already defined and just return prematurely and make it idempotent.

packages/orchestration/src/workflow/workflow-manager.ts

@@ -75,12 +75,18 @@ export class WorkflowManager {
     requiredModules?: Set<string>,
     optionalModules?: Set<string>
   ) {
-    if (WorkflowManager.workflows.has(workflowId)) {
-      throw new Error(`Workflow with id "${workflowId}" is already defined.`)
-    }
-
     const finalFlow = flow instanceof OrchestratorBuilder ? flow.build() : flow
 
+    if (WorkflowManager.workflows.has(workflowId)) {
+      const areStepsEqual =
+        JSON.stringify(finalFlow) ===
+        JSON.stringify(WorkflowManager.workflows.get(workflowId)!.flow_)
+
+      if (!areStepsEqual) {
+        throw new Error(`Workflow with id "${workflowId}" and step definition already exists.`)
+      }
+    }
+
     WorkflowManager.workflows.set(workflowId, {
       id: workflowId,
       flow_: finalFlow,