Add WorkflowExecutionState to manage execution context state

Introduce `WorkflowExecutionState` to encapsulate execution state changes for workflows. This ensures proper handling of execution flags during the lifetime of the state object and resets them upon disposal.

src/modules/Elsa.Workflows.Core/Models/WorkflowExecutionState.cs

@@ -0,0 +1,17 @@
+namespace Elsa.Workflows;
+
+internal class WorkflowExecutionState : IDisposable
+{
+    private readonly ActivityExecutionContext _activityExecutionContext;
+
+    public WorkflowExecutionState(ActivityExecutionContext activityExecutionContext)
+    {
+        _activityExecutionContext = activityExecutionContext;
+        _activityExecutionContext.IsExecuting = activityExecutionContext.WorkflowExecutionContext.IsExecuting = true;
+    }
+
+    public void Dispose()
+    {
+        _activityExecutionContext.IsExecuting = _activityExecutionContext.WorkflowExecutionContext.IsExecuting = false;
+    }
+}