Running in CI requires `spec_helper`

Due to bad ordering, where a spec would use
`fast_spec_helper` a not fully initialised environment
would be used. Ensure that `fast_spec_helper`
fallbacks to `spec_helper` in such cases

spec/fast_spec_helper.rb

 # frozen_string_literal: true
 
+# When running in CI environment, we need to load a full `spec_helper`
+if ENV['CI']
+  require_relative 'spec_helper'
+  return
+end
+
 require 'bundler/setup'
 
 ENV['GITLAB_ENV'] = 'test'