Upgrade webpack-dev-server to v4 and other webpack dependencies to latest (w/ breaking changes)

[mturley]

To keep us current and in order to address various dependabot warnings that are transitive dependencies of webpack-dev-server, this PR upgrades webpack-dev-server to v4. To ensure compatibility, all other webpack-related dependencies have also been upgraded here.

Breaking changes in major version bumps that affect us:

• clean-webpack-plugin 2.0.1 -> 4.0.0
  • 3.0.0 release notes
  • Replaced default export with named export CleanWebpackPlugin
  • 4.0.0 release notes
  • Added support for webpack 5
    • Uhh... we were already on webpack 5, so I guess we were lucky it was working?
• webpack-bundle-analyzer 3.9.0 -> 4.5.0
  • 4.0.0 release notes
  • Dropped support for Node.js 6 and 8. Minimal required version now is v10.13.0
  • Support for Webpack 5
    • Hmm...
• webpack-dev-server 3.11.2 -> 4.8.1
  • Breaking changes are described in their v4 migration guide. Changes from that guide that are relevant to us:
  • webpack-dev-server v3 and webpack-dev-server v4 automatically apply HotModuleReplacementPlugin plugin when you set hot: true, so please check you don't have HotModuleReplacementPlugin in your plugins if you have hot: true/hot: "only"
  • Minimum supported Node.js version is 12.13.0.
  • Minimum compatible webpack-cli version is 4.7.0
  • The compress option is now true by default.
  • fs, index, mimeTypes, publicPath, serverSideRender, stats, and writeToDisk (related to webpack-dev-middleware) were moved to devMiddleware option.
  • client.overlay (previously the overlay option ) is now true by default.
  • The disableHostCheck option was removed in favor allowedHosts: 'all'
  • Many CLI options were renamed in favor of the above change, please use webpack serve --help to get a list of them.
    • --progress was renamed to --client-progress