telemetry initialization and enhance event handling (#2853)

* Refactor Crew class memory initialization and enhance event handling

- Simplified the initialization of the external memory attribute in the Crew class.
- Updated memory system retrieval logic for consistency in key usage.
- Introduced a singleton pattern for the Telemetry class to ensure a single instance.
- Replaced telemetry usage in CrewEvaluator with event bus emissions for test results.
- Added new CrewTestResultEvent to handle crew test results more effectively.
- Updated event listener to process CrewTestResultEvent and log telemetry data accordingly.
- Enhanced tests to validate the singleton pattern in Telemetry and the new event handling logic.

* linted

* Remove unused telemetry attribute from Crew class memory initialization

* fix ordering of test

* Implement thread-safe singleton pattern in Telemetry class

- Introduced a threading lock to ensure safe instantiation of the Telemetry singleton.
- Updated the __new__ method to utilize double-checked locking for instance creation.

src/crewai/telemetry/telemetry.py

@@ -9,6 +9,7 @@ import warnings
 from contextlib import contextmanager
 from importlib.metadata import version
 from typing import TYPE_CHECKING, Any, Optional
+import threading
 
 from opentelemetry import trace
 from opentelemetry.exporter.otlp.proto.http.trace_exporter import (
@@ -64,6 +65,16 @@ class Telemetry:
     attribute in the Crew class.
     """
 
+    _instance = None
+    _lock = threading.Lock()
+
+    def __new__(cls):
+        if cls._instance is None:
+            with cls._lock:
+                if cls._instance is None:
+                    cls._instance = super(Telemetry, cls).__new__(cls)
+        return cls._instance
+
     def __init__(self) -> None:
         self.ready: bool = False
         self.trace_set: bool = False