PERF: Strict loading for SidebarSection queries (#21717)

What is this change required?

I noticed that actions in `SidebarSectionsController` resulted in
lots of N+1 queries problem and I wanted a solution to
prevent such problems without having to write N+1 queries tests. I have
also used strict loading for `SidebarSection` queries in performance
sensitive spots.

Note that in this commit, I have also set `config.active_record.action_on_strict_loading_violation = :log`
for the production environment so that we have more visibility of
potential N+1 queries problem in the logs. In development and test
environment, we're sticking with the default of raising an error.

config/environments/production.rb

@@ -71,4 +71,6 @@ Discourse::Application.configure do
   if ENV["RAILS_LOG_TO_STDOUT"].present?
     config.logger = ActiveSupport::TaggedLogging.new(Logger.new(STDOUT))
   end
+
+  config.active_record.action_on_strict_loading_violation = :log
 end