The logic to create additional files needed for Bazel are currently
hosted in `ng new`. Such files include the main.*.ts files needed
for AOT and a different angular.json to use Bazel builder, among others.
This commit refactors the logic into `ng add` so that it can be used to
perform the same modifications in an existing project. Users could do so
by running `ng add @angular/bazel`.
With this change, `ng new` effectively becomes an orchestrator that runs
the original `ng new` followed by `ng add @angular/bazel`.
PR Close#28436
