The current implementation for function calling with Anthropic models doesn't set `tool_calls` in AIMessage

[thiagotps]

The current implementation for function calling with Anthropic models only seems to include the available tools in the system prompt. It does not add </function_calls> to the list stop_sequences and does not make use of the stop_reason and stop_sequence values returned by the Bedrock API. Consequently, it does not add the tool_calls value in the AIMessage, as expected by LangGraph .