feat(outcomes): Tag outcome metric with data category (#19661)

src/sentry/utils/outcomes.py

@@ -176,5 +176,9 @@ def track_outcome(
     metrics.incr(
         "events.outcomes",
         skip_internal=True,
-        tags={"outcome": outcome.name.lower(), "reason": reason},
+        tags={
+            "outcome": outcome.name.lower(),
+            "reason": reason,
+            "category": category.api_name() if category is not None else "null",
+        },
     )