Use webpack config js package in everything except Jetpack (#21580)

* lazy-images: Use the new webpack-config package

  Mostly as a proof of concept. But I also took the opportunity to clean a
  few things up:

  * Name the built JS as ".min.js" like it should be.
  * Use copy-webpack-plugin to copy the src version of
    intersection-observer.
  * Use @wordpress/dependency-extraction-webpack-plugin to handle the
    cache-buster version in `wp_enqueue_script()`.

* connection-ui: Use the new webpack-config package

  I tried not to change too much in this iteration, but I do note that the
  new package uses a newer version of @wordpress/browserslist-config than
  calyspo-build does so it now transpiles without IE11 support.

* identity-crisis: Use the new webpack-config package

  I tried not to change too much in this iteration, but I do note that the
  new package uses a newer version of @wordpress/browserslist-config than
  calyspo-build does so it now transpiles without IE11 support.

  Also I dropped babel-minify-webpack-plugin, as terser that's included
  with webpack seems to work just as well (and has been updated more
  recently than 4 years ago).

* jitm: Use the new webpack-config package

  This results in no change to the production build. The development build
  is no longer actually minified.

* backup: Use the new webpack-config package

  This also reverts the "bring back the "Cloud" icon, the path changed
  after the Webpack update" bit from #20900 and similar code. The
  problem was Automattic/wp-calypso#56111, which is not present in the
  new package.

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/1426089502

CHANGELOG.md

@@ -5,6 +5,13 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [2.0.5-alpha] - unreleased
+
+This is an alpha version! The changes listed here are not final.
+
+### Changed
+- Update webpack build config.
+
 ## [2.0.4] - 2021-11-02
 ### Changed
 - Set `convertDeprecationsToExceptions` true in PHPUnit config.
@@ -128,6 +135,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Lazy Images: Move into a package
 
+[2.0.5-alpha]: https://github.com/Automattic/jetpack-lazy-images/compare/v2.0.4...v2.0.5-alpha
 [2.0.4]: https://github.com/Automattic/jetpack-lazy-images/compare/v2.0.3...v2.0.4
 [2.0.3]: https://github.com/Automattic/jetpack-lazy-images/compare/v2.0.2...v2.0.3
 [2.0.2]: https://github.com/Automattic/jetpack-lazy-images/compare/v2.0.1...v2.0.2

dist/intersection-observer.min.asset.php

@@ -0,0 +1 @@
+<?php return array('dependencies' => array(), 'version' => '3ca22a168a1e1d85e6101f2960316103');