chore(antithesis): Track dropped transactions in as sometimes! assertion

It should be the case that for particularly extreme situations ADP will
drop transactions. We are currently unable to see this in-rig except by
implication. This commit adds a sometimes! assertion to give visibility
into this.

Author: blt

lib/saluki-components/src/common/datadog/io.rs

@@ -691,6 +691,17 @@ fn generate_retry_queue_id(context: ComponentContext, endpoint: &ResolvedEndpoin
 }
 
 fn track_queue_drops(telemetry: &ComponentTelemetry, domain: &str, push_result: PushResult) {
+    saluki_antithesis::sometimes!(
+        push_result.had_drops(),
+        "ADP dropped transactions it could not deliver",
+        {
+            "domain": domain,
+            "items_dropped": push_result.items_dropped,
+            "events_dropped": push_result.events_dropped,
+            "data_points_dropped": push_result.data_points_dropped
+        }
+    );
+
     telemetry.track_dropped_items(push_result.items_dropped);
     telemetry.track_dropped_events(push_result.events_dropped);
     telemetry.track_data_points_dropped(domain, push_result.data_points_dropped);