Refactor workflow instance creation and execution logic. (#6586)

Updated `CreateAndRunInstanceAsync` to separate instance creation and execution with locking to handle nested workflow scenarios. Made `RunInstanceAsync` public to facilitate reuse in the distributed workflow client.

src/modules/Elsa.Workflows.Runtime.Distributed/Services/DistributedWorkflowClient.cs

@@ -31,8 +31,27 @@ public class DistributedWorkflowClient(
 
     public async Task<RunWorkflowInstanceResponse> CreateAndRunInstanceAsync(CreateAndRunWorkflowInstanceRequest request, CancellationToken cancellationToken = default)
     {
-        var result = await _localWorkflowClient.CreateAndRunInstanceAsync(request, cancellationToken);
-        return result;
+        var createRequest = new CreateWorkflowInstanceRequest
+        {
+            Properties = request.Properties,
+            CorrelationId = request.CorrelationId,
+            Name = request.Name,
+            Input = request.Input,
+            WorkflowDefinitionHandle = request.WorkflowDefinitionHandle,
+            ParentId = request.ParentId
+        };
+        var workflowInstance = await _localWorkflowClient.CreateInstanceInternalAsync(createRequest, cancellationToken);
+        
+        // We need to lock newly created workflow instances too, because it might dispatch child workflows that attempt to resume the parent workflow.
+        // For example, when using a DispatchWorkflow activity configured to wait for the dispatched workflow to complete.
+        return await WithLockAsync(async () => await _localWorkflowClient.RunInstanceAsync(workflowInstance, new()
+        {
+            Input = request.Input,
+            Variables = request.Variables,
+            Properties = request.Properties,
+            TriggerActivityId = request.TriggerActivityId,
+            ActivityHandle = request.ActivityHandle
+        }, cancellationToken));
     }
 
     public async Task CancelAsync(CancellationToken cancellationToken = default)

src/modules/Elsa.Workflows.Runtime/Services/LocalWorkflowClient.cs

@@ -104,7 +104,7 @@ public class LocalWorkflowClient(
         return workflowInstanceManager.ExistsAsync(workflowInstanceId, cancellationToken);
     }
 
-    private async Task<RunWorkflowInstanceResponse> RunInstanceAsync(WorkflowInstance workflowInstance, RunWorkflowInstanceRequest request, CancellationToken cancellationToken = default)
+    public async Task<RunWorkflowInstanceResponse> RunInstanceAsync(WorkflowInstance workflowInstance, RunWorkflowInstanceRequest request, CancellationToken cancellationToken = default)
     {
         var workflowState = workflowInstance.WorkflowState;