test(relay): Instrument flaky test (#75361)

`test_histogram_outliers` became flaky after
getsentry/relay#3863.

Add info to the assert to get more insights.

tests/relay_integration/test_metrics_extraction.py

@@ -1,3 +1,4 @@
+import time
 import uuid
 
 import confluent_kafka as kafka
@@ -148,11 +149,14 @@ def test_histogram_outliers(self):
  self.post_and_retrieve_event(event_data)
 
  histogram_outlier_tags = {}
- for _ in range(1000):
+ buckets = []
+ t0 = time.monotonic()
+ for attempt in range(1000):
  message = consumer.poll(timeout=1.0)
  if message is None:
  break
  bucket = json.loads(message.value())
+ buckets.append(bucket)
  try:
  histogram_outlier_tags[bucket["name"]] = bucket["tags"]["histogram_outlier"]
  except KeyError:
@@ -163,4 +167,8 @@ def test_histogram_outliers(self):
  "d:transactions/duration@millisecond": "inlier",
  "d:transactions/measurements.fcp@millisecond": "outlier",
  "d:transactions/measurements.lcp@millisecond": "inlier",
+ }, {
+ "attempts": attempt,
+ "time_elapsed": time.monotonic() - t0,
+ "bucket_count": len(buckets),
  }