Instrument `@langchain/langgraph` in accordance to Agentic AI spec

[amychisholm03]

Description

There is a customer and internal request to instrument @langchain/langgraph. This instrumentation must utilize the LlmEvents: LlmTool (currently only used in @langchain/core instrumentation) and the new LlmAgent event, introduced in this pending spec. The coordinating segments, Llm/tool/{vendor_name}/{function_name}/{tool_name} and Llm/agent/{vendor_name}/{function_name}/{agent_name} must be created.

Customer request:
Agent should instrument the framework methods according to the Agentic spec:

• It should be possible to measure agent’s latency, errors and tokens
• It should be able to monitor agent calls to LLM/Tool/Agent
• It should be able to detect there was an agent call within the span
• It should be possible to view agent to agent calls within entity map

Acceptance Criteria

• LlmTool event is created for tool calls
• LlmAgent event is created for agent functions
• Coordinating spans, Llm/tool and Llm/agent, are created

Additional context

• Related spec is currently in PR review
• Jira link

[Newrelic-Boomi]

https://new-relic.atlassian.net/browse/NR-499523