Display diff stats on Rapid Diffs

...assets/javascripts/diffs/components/diff_app_controls.vue

app/assets/javascripts/diffs/components/diff_stats.vue

app/assets/javascripts/rapid_diffs/app/index.js

app/assets/javascripts/rapid_diffs/app/init_file_browser.js

app/assets/javascripts/rapid_diffs/app/view_settings.js

app/assets/javascripts/rapid_diffs/stores/diffs_view.js

app/components/rapid_diffs/app_component.html.haml

locale/gitlab.pot

spec/components/rapid_diffs/app_component_spec.rb

spec/frontend/rapid_diffs/app/app_spec.js

spec/frontend/rapid_diffs/app/init_file_browser_spec.js

spec/frontend/rapid_diffs/app/view_settings_spec.js

spec/frontend/rapid_diffs/stores/diffs_view_spec.js