Merge branch '18593-autofilter-rinku-instrumentation' into 'master'

Instrument Rinku usage

## What does this MR do?

Add metrics instrumentation to Rinku, module methods (autolink)

## What are the relevant issue numbers?

#18593 

## 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~~
  - [x] 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 !5063

CHANGELOG

@@ -32,6 +32,7 @@ v 8.10.0 (unreleased)
   - Better caching of git calls on ProjectsController#show.
   - Add API endpoint for a group issues !4520 (mahcsig)
   - Add Bugzilla integration !4930 (iamtjg)
+  - Instrument Rinku usage
   - Metrics for Rouge::Plugins::Redcarpet and Rouge::Formatters::HTMLGitlab
   - RailsCache metris now includes fetch_hit/fetch_miss and read_hit/read_miss info.
   - Allow [ci skip] to be in any case and allow [skip ci]. !4785 (simon_w)

config/initializers/metrics.rb

@@ -135,6 +135,8 @@ if Gitlab::Metrics.enabled?
 
     config.instrument_instance_methods(Rouge::Plugins::Redcarpet)
     config.instrument_instance_methods(Rouge::Formatters::HTMLGitlab)
+
+    config.instrument_methods(Rinku)
   end
 
   GC::Profiler.enable