Merge branch 'fix/request-profiler-middleware-error-on-reload' into 'master'

Fix RequestProfiler::Middleware error when code is reloaded in development

## What does this MR do?
It explicitly requires `Gitlab::RequestProfiler::Middleware` before inserting it in the stack instead of autoloading it.

## Are there points in the code the reviewer needs to double check?
N/A

## Why was this MR needed?
It fixes #20452

## What are the relevant issue numbers?
#20452 

## Screenshots (if relevant)
N/A

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] ~~[Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)~~
- [ ] ~~API support added~~
- ~~Tests~~
  - [ ] ~~Added for this feature/bug~~
  - [ ] ~~All builds are passing~~
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5593

CHANGELOG

@@ -43,6 +43,7 @@ v 8.11.0 (unreleased)
   - Change requests_profiles resource constraint to catch virtually any file
   - Reduce number of queries made for merge_requests/:id/diffs
   - Sensible state specific default sort order for issues and merge requests !5453 (tomb0y)
+  - Fix RequestProfiler::Middleware error when code is reloaded in development
 
 v 8.10.3 (unreleased)
   - Fix importer for GitHub Pull Requests when a branch was removed

config/initializers/request_profiler.rb

+require 'gitlab/request_profiler/middleware'
+
 Rails.application.configure do |config|
   config.middleware.use(Gitlab::RequestProfiler::Middleware)
 end

lib/gitlab/request_profiler/middleware.rb

 require 'ruby-prof'
+require 'gitlab/request_profiler'
 
 module Gitlab
   module RequestProfiler