feat: Add instrumentation for nodestore event type (#84800)

- This adds a tag that will let us know what kind of event is being
retrieved from nodestore so we can monitor transaction usage in
nodestore

Author: wmak

src/sentry/eventstore/snuba/backend.py

@@ -362,6 +362,9 @@ def get_event_by_id(
         if len(event.data) == 0:
             return None
 
+        if group_id is not None:
+            sentry_sdk.set_tag("nodestore.event_type", event.get_event_type())
+
         if group_id is not None and (
             event.get_event_type() == "error"
             or (event.get_event_type() == "transaction" and skip_transaction_groupevent)