telemetry: include user decisions in tool call logs (#966)

Add the user's decision (accept, reject, modify) to tool call telemetry to better understand user intent. The decision provides crucial context to the `success` metric, as a user can reject a call that would have succeeded or accept one that fails. 

Also prettify the arguments json.

Example: 
![image](https://github.com/user-attachments/assets/251cb9fc-ceaa-4cdd-929c-8de47031aca8)

#750

packages/core/src/telemetry/metrics.ts

@@ -89,6 +89,7 @@ export function recordToolCallMetrics(
   functionName: string,
   durationMs: number,
   success: boolean,
+  decision?: 'accept' | 'reject' | 'modify',
 ): void {
   if (!toolCallCounter || !toolCallLatencyHistogram || !isMetricsInitialized)
     return;
@@ -97,6 +98,7 @@ export function recordToolCallMetrics(
     ...getCommonAttributes(config),
     function_name: functionName,
     success,
+    decision,
   };
   toolCallCounter.add(1, metricAttributes);
   toolCallLatencyHistogram.record(durationMs, {