Add task decomposition feature (Issue #2717)

This PR implements task decomposition as requested in Issue #2717.
It allows complex tasks to be automatically split into sub-tasks
without manual intervention.

- Added parent_task and sub_tasks fields to Task class
- Implemented decompose() method to create sub-tasks
- Added combine_sub_task_results() method to aggregate results
- Updated execute_sync() to handle sub-task execution
- Added execute_sub_tasks_async() for asynchronous execution
- Created tests for the task decomposition functionality
- Added example script demonstrating usage

Co-Authored-By: Joe Moura <joao@crewai.com>

examples/task_decomposition_example.py

@@ -0,0 +1,48 @@
+"""
+Example of using task decomposition in CrewAI.
+
+This example demonstrates how to use the task decomposition feature
+to break down complex tasks into simpler sub-tasks.
+"""
+
+from crewai import Agent, Task, Crew
+
+researcher = Agent(
+    role="Researcher",
+    goal="Research effectively",
+    backstory="You're an expert researcher with skills in breaking down complex topics.",
+)
+
+research_task = Task(
+    description="Research the impact of AI on various industries",
+    expected_output="A comprehensive report covering multiple industries",
+    agent=researcher,
+)
+
+sub_tasks = research_task.decompose(
+    descriptions=[
+        "Research AI impact on healthcare industry",
+        "Research AI impact on finance industry",
+        "Research AI impact on education industry",
+    ],
+    expected_outputs=[
+        "A report on AI in healthcare",
+        "A report on AI in finance",
+        "A report on AI in education",
+    ],
+    names=["Healthcare", "Finance", "Education"],
+)
+
+crew = Crew(
+    agents=[researcher],
+    tasks=[research_task],
+)
+
+result = crew.kickoff()
+print(result)
+
+
+# 
+#     
+#     
+#