Also use it to test the public API for core and common
Once we have an ng_package for every package, we can remove
the npm dependency on ts-api-guardian and the gulp-based
public api check.
PR Close#22544
* 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
