feat(metrics): metrics meta support for gauges (#59106)

src/sentry/snuba/metrics/datasource.py

@@ -203,11 +203,18 @@ def get_stored_mris(projects: Sequence[Project], use_case_id: UseCaseID) -> List
             EntityKey.MetricsSets,
             EntityKey.MetricsDistributions,
         }
+    elif use_case_id == UseCaseID.TRANSACTIONS:
+        entity_keys = {
+            EntityKey.GenericMetricsCounters,
+            EntityKey.GenericMetricsSets,
+            EntityKey.GenericMetricsDistributions,
+        }
     else:
         entity_keys = {
             EntityKey.GenericMetricsCounters,
             EntityKey.GenericMetricsSets,
             EntityKey.GenericMetricsDistributions,
+            EntityKey.GenericMetricsGauges,
         }
 
     stored_metrics = []

src/sentry/snuba/metrics/fields/base.py

@@ -194,6 +194,7 @@ def _get_known_entity_of_metric_mri(metric_mri: str) -> Optional[EntityKey]:
                 "c": EntityKey.GenericMetricsCounters,
                 "d": EntityKey.GenericMetricsDistributions,
                 "s": EntityKey.GenericMetricsSets,
+                "g": EntityKey.GenericMetricsGauges,
             }[entity_prefix]
     except (ValueError, IndexError, KeyError):
         pass