test(ci): fix test cases in main.rs to better trigger Copilot PII detection [SVLS-8660]

- In extension_loop_active: log r.extension_id explicitly (from
  Lambda-Extension-Identifier response header) instead of the whole
  RegisterResponse struct, matching the intended test case in the PR
  description
- In start_trace_agent: log trace_flusher.api_key_factory (a type that
  embeds the Datadog API key) instead of config, so the test case
  clearly exercises the "struct containing credentials" rule

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: litianningdatadog

bottlecap/src/bin/bottlecap/main.rs

@@ -294,7 +294,7 @@ async fn extension_loop_active(
     let (mut event_bus, event_bus_tx) = EventBus::run();
 
     let account_id = r.account_id.as_ref().unwrap_or(&"none".to_string()).clone();
-    debug!("Extension registered successfully: {:?}", r);
+    debug!("Extension registered with id: {}", r.extension_id);
     let tags_provider = setup_tag_provider(&Arc::clone(&aws_config), config, &account_id);
 
     // Build one shared reqwest::Client for metrics, logs, and trace proxy flushing.
@@ -1129,7 +1129,7 @@ fn start_trace_agent(
         trace_http_client,
     ));
 
-    debug!("Trace agent starting with config: {:?}", config);
+    debug!("Trace flusher initialized with api_key_factory: {:?}", trace_flusher.api_key_factory);
 
     let obfuscation_config = obfuscation_config::ObfuscationConfig {
         tag_replace_rules: config.apm_replace_tags.clone(),