Add suggest pipeline experiment feature flag

- this is an incremental overall change and this
  will be the first step in getting the experiment implemented.

app/controllers/projects/merge_requests_controller.rb

@@ -21,6 +21,7 @@ class Projects::MergeRequestsController < Projects::MergeRequests::ApplicationCo
   before_action only: [:show] do
     push_frontend_feature_flag(:diffs_batch_load, @project)
     push_frontend_feature_flag(:single_mr_diff_view, @project)
+    push_frontend_feature_flag(:suggest_pipeline) if experiment_enabled?(:suggest_pipeline)
   end
 
   before_action do

lib/gitlab/experimentation.rb

@@ -22,6 +22,12 @@ module Gitlab
         environment: ::Gitlab.dev_env_or_com?,
         enabled_ratio: 0.25,
         tracking_category: 'Growth::Acquisition::Experiment::PaidSignUpFlow'
+      },
+      suggest_pipeline: {
+        feature_toggle: :suggest_pipeline,
+        environment: ::Gitlab.dev_env_or_com?,
+        enabled_ratio: 0.1,
+        tracking_category: 'Growth::Expansion::Experiment::SuggestPipeline'
       }
     }.freeze