feat(escalating-issues): Only send generic metrics events for errors (#56407)

## Objective:
We do not need to send metrics to the Generic Metrics Backend for
non-error event types.

src/sentry/tasks/post_process.py

@@ -592,7 +592,10 @@ def post_process_group(
         update_event_groups(event, group_states)
         bind_organization_context(event.project.organization)
         _capture_event_stats(event)
-        if features.has("organizations:escalating-metrics-backend", event.project.organization):
+        if (
+            features.has("organizations:escalating-metrics-backend", event.project.organization)
+            and not is_transaction_event
+        ):
             _update_escalating_metrics(event)
 
         group_events: Mapping[int, GroupEvent] = {

tests/sentry/tasks/test_post_process.py

@@ -1759,6 +1759,32 @@ class PostProcessGroupErrorTest(
         )
         return cache_key
 
+    @with_feature("organizations:escalating-metrics-backend")
+    @patch("sentry.sentry_metrics.client.generic_metrics_backend.counter")
+    def test_generic_metrics_backend_counter(self, generic_metrics_backend_mock):
+        min_ago = iso_format(before_now(minutes=1))
+        event = self.create_event(
+            data={
+                "exception": {
+                    "values": [
+                        {
+                            "type": "ZeroDivisionError",
+                            "stacktrace": {"frames": [{"function": f} for f in ["a", "b"]]},
+                        }
+                    ]
+                },
+                "timestamp": min_ago,
+                "start_timestamp": min_ago,
+                "contexts": {"trace": {"trace_id": "b" * 32, "span_id": "c" * 16, "op": ""}},
+            },
+            project_id=self.project.id,
+        )
+        self.call_post_process_group(
+            is_new=True, is_regression=False, is_new_group_environment=True, event=event
+        )
+
+        assert generic_metrics_backend_mock.call_count == 1
+
 
 @region_silo_test
 class PostProcessGroupPerformanceTest(
@@ -1804,6 +1830,7 @@ class PostProcessGroupPerformanceTest(
             )
         return cache_key
 
+    @patch("sentry.sentry_metrics.client.generic_metrics_backend.counter")
     @patch("sentry.tasks.post_process.run_post_process_job")
     @patch("sentry.rules.processor.RuleProcessor")
     @patch("sentry.signals.transaction_processed.send_robust")
@@ -1814,6 +1841,7 @@ class PostProcessGroupPerformanceTest(
         transaction_processed_signal_mock,
         mock_processor,
         run_post_process_job_mock,
+        generic_metrics_backend_mock,
     ):
         min_ago = before_now(minutes=1).replace(tzinfo=timezone.utc)
         event = self.store_transaction(
@@ -1838,6 +1866,7 @@ class PostProcessGroupPerformanceTest(
         assert event_processed_signal_mock.call_count == 0
         assert mock_processor.call_count == 0
         assert run_post_process_job_mock.call_count == 0
+        assert generic_metrics_backend_mock.call_count == 0
 
     @patch("sentry.tasks.post_process.handle_owner_assignment")
     @patch("sentry.tasks.post_process.handle_auto_assignment")