fix(eventstore): add index to reduce db workload (#2813)

migrations/cockroach/V1.102__event_idx.sql

@@ -0,0 +1,15 @@
+CREATE INDEX agg_type_seq ON eventstore.events 
+    (aggregate_type, event_sequence DESC) 
+STORING (
+    id
+    , event_type
+    , aggregate_id
+    , aggregate_version
+    , previous_aggregate_sequence
+    , creation_date
+    , event_data
+    , editor_user
+    , editor_service
+    , resource_owner
+    , previous_aggregate_type_sequence
+);