For consideration.

These warnings are already covered by renderers based on react-reconciler. Maybe we don't gain that much by mirroring them in the shallow renderer? Maybe it's not worth the added complexity? Particularly with more complicated warnings like the ones being added for #12419 and #12404.
/**
 * Copyright (c) 2013-present, Facebook, Inc.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @emails react-core
 * @jest-environment node
 */
'use strict';
let createRenderer;
let PropTypes;
let React;
describe('ReactShallowRenderer', () => {
  beforeEach(() => {
    jest.resetModules();
    createRenderer = require('react-test-renderer/shallow').createRenderer;
    PropTypes = require('prop-types');
    React = require('react');
  });
  it('should call all of the legacy lifecycle hooks', () => {
    const logs = [];
    const logger = message => () => logs.push(message) || true;
    class SomeComponent extends React.Component {