fix: replace nonexistent trace_tool_response with trace_merged_tool_calls in ADK patch

[MaxwellCalkin]

Summary

Fix Google ADK instrumentation error on startup:

Could not wrap google.adk.telemetry.trace_tool_response: module 'google.adk.telemetry' has no attribute 'trace_tool_response'

Fixes #1257.

Problem

google.adk.telemetry.trace_tool_response does not exist in any supported version of google-adk (1.4.1+). The function was renamed to trace_merged_tool_calls with a different signature:

# Old (nonexistent):
trace_tool_response(invocation_context, event_id, function_response_event)

# Current:
trace_merged_tool_calls(response_event_id, function_response_event)

Additionally, _adk_trace_tool_call_wrapper incorrectly extracts args[0] as the tool arguments dict when it is actually the tool object. The current trace_tool_call signature is:

trace_tool_call(tool: BaseTool, args: dict, function_response_event: Event)

Changes

• Replace _adk_trace_tool_response_wrapper with _adk_trace_merged_tool_calls_wrapper matching the trace_merged_tool_calls(response_event_id, function_response_event) signature
• Fix _adk_trace_tool_call_wrapper to correctly extract the tool object from args[0] and tool arguments from args[1]
• Update patch_adk() to wrap trace_merged_tool_calls instead of trace_tool_response

Test plan

• Verify no more "Could not wrap trace_tool_response" warning on startup with google-adk >= 1.4.1
• Verify tool call and merged tool call attributes are correctly set on spans
• Verify existing ADK instrumentation continues to work (agent spans, LLM spans, tool spans)

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