Refactor project delete modal

Implementation guide

1. Move app/assets/javascripts/vue_shared/components/projects_list/project_list_item_delayed_deletion_modal_footer.vue directly into app/assets/javascripts/projects/components/shared/delete_modal.vue to replace modal-footer.
2. Remove modal-footer slot from app/assets/javascripts/projects/components/project_delayed_delete_button.vue
3. Check if stats are Number type. If they are, use numberToMetricPrefix to format, same as what we do in app/assets/javascripts/vue_shared/components/projects_list/projects_list_item.vue.