feat: add support for streaming tool call events

[greysonlalonde]

Supports #3982

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Note

Introduces provider-agnostic streaming tool-call events and instrumentation.

• Adds call_type and tool_call data to _emit_stream_chunk_event in BaseLLM to distinguish text vs tool chunks
• Emits LLMCallType.TOOL_CALL stream events with {id, function{name, arguments}, type, index} across providers:
  • Anthropic: tracks tool-use blocks by content index; streams partial input_json_delta arguments
  • Azure/OpenAI: accumulates tool-call args keyed by sequential index; emits incremental chunks with consistent ids
  • Bedrock: tracks toolUse start/delta/stop, accumulates input, emits tool-call chunks; minor typing/message formatting cleanups
  • Gemini: streams function_call parts, assigns unique call ids, emits args as JSON
• Updates structured-output handling where needed (e.g., Gemini tool param passing)
• Adds comprehensive tests and VCR cassettes validating event shape, argument accumulation, id consistency, and text vs tool differentiation

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[lucasgomide]

Can you add some tests?

[cursor]

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