feat(events_stream): Add document_event_number column to events_stream_v1 tables (DENG-9800).

Author: sean-rose

sql_generators/glean_usage/templates/events_stream_v1.query.sql

@@ -135,10 +135,12 @@ SELECT
   event.name AS event_name,
   ARRAY_TO_STRING([event.category, event.name], '.') AS event, -- handles NULL values better
   from_map_event_extra(event.extra) AS event_extra,
+  (event_offset + 1) AS document_event_number,
 FROM
   base
 CROSS JOIN
   UNNEST(events) AS event
+  WITH OFFSET AS event_offset
   {% if app_name == "firefox_desktop" %}
     WHERE
       -- See https://mozilla-hub.atlassian.net/browse/DENG-7513