React: Restore umd builds (#63602)

Co-authored-by: youknowriad <youknowriad@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>
Co-authored-by: tyxla <tyxla@git.wordpress.org>

tools/webpack/packages.js

@@ -102,6 +102,13 @@ const exportDefaultPackages = [
 	'warning',
 ];
 
+const copiedVendors = {
+	'react.js': 'react/umd/react.development.js',
+	'react.min.js': 'react/umd/react.production.min.js',
+	'react-dom.js': 'react-dom/umd/react-dom.development.js',
+	'react-dom.min.js': 'react-dom/umd/react-dom.production.min.js',
+};
+
 module.exports = {
 	...baseConfig,
 	name: 'packages',
@@ -148,7 +155,13 @@ module.exports = {
 					transform: stylesTransform,
 					noErrorOnMissing: true,
 				} ) )
-				.concat( bundledPackagesPhpConfig ),
+				.concat( bundledPackagesPhpConfig )
+				.concat(
+					Object.entries( copiedVendors ).map( ( [ to, from ] ) => ( {
+						from: `node_modules/${ from }`,
+						to: `build/vendors/${ to }`,
+					} ) )
+				),
 		} ),
 		new MomentTimezoneDataPlugin( {
 			startYear: 2000,

tools/webpack/vendors.js

@@ -4,8 +4,6 @@
 const { join } = require( 'path' );
 
 const importedVendors = {
-	react: { import: 'react', global: 'React' },
-	'react-dom': { import: 'react-dom', global: 'ReactDOM' },
 	'react-jsx-runtime': {
 		import: 'react/jsx-runtime',
 		global: 'ReactJSXRuntime',
@@ -35,12 +33,9 @@ module.exports = [
 					},
 				},
 
-				externals:
-					name === 'react'
-						? {}
-						: {
-								react: 'React',
-						  },
+				externals: {
+					react: 'React',
+				},
 			};
 		} );
 	} ),