test(node): Fix flaky Anthropic integration test (#21034)

This particular test was looking up the completion span by matching on
`GEN_AI_INPUT_MESSAGES_ATTRIBUTE` which is not unique. Four spans have
that same input message, with varying span ordering, the find lookup
could match on the wrong span which lacked `max_tokens`.

The fix is to find th espan by `GEN_AI_RESPONSE_ID_ATTRIBUTE` which
identifies the span better.

Closes: #21029

Author: andreiborza

dev-packages/node-integration-tests/suites/tracing/anthropic/test.ts

@@ -210,9 +210,7 @@ describe('Anthropic integration', () => {
           span: container => {
             expect(container.items).toHaveLength(5);
             const completionSpan = container.items.find(
-              span =>
-                span.attributes[GEN_AI_INPUT_MESSAGES_ATTRIBUTE]?.value ===
-                '[{"role":"user","content":"What is the capital of France?"}]',
+              span => span.attributes[GEN_AI_RESPONSE_ID_ATTRIBUTE]?.value === 'msg_mock123',
             );
             expect(completionSpan).toBeDefined();
             expect(completionSpan!.name).toBe('chat claude-3-haiku-20240307');
@@ -224,6 +222,9 @@ describe('Anthropic integration', () => {
             expect(completionSpan!.attributes[GEN_AI_RESPONSE_MODEL_ATTRIBUTE].value).toBe('claude-3-haiku-20240307');
             expect(completionSpan!.attributes[GEN_AI_RESPONSE_ID_ATTRIBUTE].value).toBe('msg_mock123');
             expect(completionSpan!.attributes[GEN_AI_RESPONSE_TEXT_ATTRIBUTE].value).toBe('Hello from Anthropic mock!');
+            expect(completionSpan!.attributes[GEN_AI_INPUT_MESSAGES_ATTRIBUTE].value).toBe(
+              '[{"role":"user","content":"What is the capital of France?"}]',
+            );
             expect(completionSpan!.attributes[GEN_AI_SYSTEM_ATTRIBUTE].value).toBe('anthropic');
             expect(completionSpan!.attributes[GEN_AI_USAGE_INPUT_TOKENS_ATTRIBUTE].value).toBe(10);
             expect(completionSpan!.attributes[GEN_AI_USAGE_OUTPUT_TOKENS_ATTRIBUTE].value).toBe(15);