feat: Add LLM call events for improved observability (#2214)

* feat: Add LLM call events for improved observability

- Introduce new LLM call events: LLMCallStartedEvent, LLMCallCompletedEvent, and LLMCallFailedEvent
- Emit events for LLM calls and tool calls to provide better tracking and debugging
- Add event handling in the LLM class to track call lifecycle
- Update event bus to support new LLM-related events
- Add test cases to validate LLM event emissions

* feat: Add event handling for LLM call lifecycle events

- Implement event listeners for LLM call events in EventListener
- Add logging for LLM call start, completion, and failure events
- Import and register new LLM-specific event types

* less log

* refactor: Update LLM event response type to support Any

* refactor: Simplify LLM call completed event emission

Remove unnecessary LLMCallType conversion when emitting LLMCallCompletedEvent

* refactor: Update LLM event docstrings for clarity

Improve docstrings for LLM call events to more accurately describe their purpose and lifecycle

* feat: Add LLMCallFailedEvent emission for tool execution errors

Enhance error handling by emitting a specific event when tool execution fails during LLM calls

src/crewai/utilities/events/__init__.py

@@ -34,6 +34,7 @@ from .tool_usage_events import (
     ToolUsageEvent,
     ToolValidateInputErrorEvent,
 )
+from .llm_events import LLMCallCompletedEvent, LLMCallFailedEvent, LLMCallStartedEvent
 
 # events
 from .event_listener import EventListener