…local packages (#35858)

In some cases, we want to test the AIO app or docs examples against the
locally built Angular packages (for example to ensure that the changes
in a commit do not introduce a breaking change). In order to achieve
this, we have the `ng-packages-installer` script that handles updating
a project's `package.json` file to use the locally built Angular
packages (and appropriate versions for their (dev-/peer-)dependencies).

Previously, `ng-packages-installer` would only consider the locally
built Angular packages (from `dist/packages-dist/`). However, given that
Zone.js is now part of the `angular/angular` repo, it makes sense to
also use the locally built Zone.js package (from `dist/zone.js-dist/`).
Otherwise, the tests might fail for commits that update both the Angular
packages (and related docs examples) and the Zone.js package. An example
of such a simultaneous change (that would have broken tests) is #33838.

This commit updates the script to install the locally built Zone.js
package (in addition to the Angular ones). The commit ensures that the
Zone.js package will always be available alongside the Angular packages
(i.e. that the Zone.js package will be built by the same script that
builds the Angular packages and that the `dist/zone.js-dist/` directory
will be cached on CI).

Note: This problem was discovered while enabling docs examples unit
tests in #34374.

PR Close #35858