build: publish tree of files rather than FESMs (#18541)

* Remove now unnecessary portions of build.
* Add a compilePackageES5 method to build ES5 from sources
* Rework all package.json and rollup config files to new format
* Remove "extends" from tsconfig-build.json files and fixup compilation roots

PR Close #18541

tools/gulp-tasks/format.js

@@ -17,6 +17,9 @@ const srcsToFmt = [
   'tools/**/*.{js,ts}',
   '!tools/public_api_guard/**/*.d.ts',
   './*.{js,ts}',
+  '!**/node_modules/**',
+  '!**/dist/**',
+  '!**/built/**',
   '!shims_for_IE.js',
   `!${I18N_DATA_FOLDER}/**/*.{js,ts}`,
   `!${I18N_FOLDER}/available_locales.ts`,