Add backtraces to Peek performance bar for SQL calls

Just as we have backtraces for Gitaly, we should also have backtraces
for SQL calls. This makes it much easier to find the source of the SQL
call and optimize N+1 queries and other performance issues with an
endpoint.

changelogs/unreleased/sh-add-backtrace-to-sql-queries.yml

+---
+title: Add backtraces to Peek performance bar for SQL calls
+merge_request:
+author:
+type: added

lib/gitlab/performance_bar/peek_query_tracker.rb

@@ -27,15 +27,16 @@ module Gitlab
         subscribe('sql.active_record') do |_, start, finish, _, data|
           if Gitlab::SafeRequestStore.store[:peek_enabled]
             unless data[:cached]
-              track_query(data[:sql].strip, data[:binds], start, finish)
+              backtrace = Gitlab::Profiler.clean_backtrace(caller)
+              track_query(data[:sql].strip, data[:binds], backtrace, start, finish)
             end
           end
         end
       end
 
-      def track_query(raw_query, bindings, start, finish)
+      def track_query(raw_query, bindings, backtrace, start, finish)
         duration = (finish - start) * 1000.0
-        query_info = { duration: duration.round(3), sql: raw_query }
+        query_info = { duration: duration.round(3), sql: raw_query, backtrace: backtrace }
 
         PEEK_DB_CLIENT.query_details << query_info
       end