Handle `select_one` queries in database load balancing

We have `select` going to the secondary, and `select_all` optionally
going to the secondary, but `select_one` (using for methods like `any?`)
was going to a primary via `method_missing`.

Similarly, if we're handling `quote_column_name`, we should treat
`sanitize_limit` in the same way.

ee/lib/gitlab/database/load_balancing/connection_proxy.rb

@@ -24,7 +24,9 @@ module Gitlab
         ).freeze
 
         NON_STICKY_READS = %i(
+          sanitize_limit
           select
+          select_one
           quote_column_name
         ).freeze