Manually execute `ng new` deps postinstall scripts

# 🚀 Feature request

### Command (mark with an `x`)

- [X] new

### Description

Currently, `ng new` will automatically run `npm install` which (if the user has not disabled it), automatically runs all postinstall scripts. This can be a vulnerability since any compromised package in the NPM dependency graph could add a postinstall step to install malware on developer machines.

### Describe the solution you'd like

We could reduce the attack surface by disabling postinstall on the automatic `npm install` and then manually invoke the postinstall for a known set of required packages. Only 3 packages currently use postinstall steps, so limiting execution to just those would significantly reduce the attack surface for a potential supply chain attack.

One possible concern is for dependencies which add a required postinstall step in the future. We can pretty easily add a test to make sure we aren't missing any postinstall steps from our transitive dependencies, though this inherently breaks abstraction somewhat. Adding a postinstall step is (somewhat debate-ably) a breaking change, so any package which adds one in the future should require a major version bump where we have an opportunity to allowlist it.

The one edge case I can think of is if we have:

```
ng-new-app@0.0.0 -> package-a@^1.0.0 -> package-b@^1.0.0
```

And `package-b` gets a new postinstall step in `v2.0.0`. However, `package-a` may be able to manage the breakage without violating their own public API (or maybe doesn't notice the new postinstall step) and simply bumps to `v1.0.1`. This would immediately be pulled in to the next `ng new` command and fail. I think such a scenario would actually be a bad patch release for `package-a`, since adding a required postinstall step is fundamentally a breaking change. We would rely on NPM package maintainers to make the right semver-compatible decisions for a somewhat nuanced case, but this is probably better than the alternative.

Empieza examinando el flujo de ng new que ejecuta automáticamente npm install y determina cómo se gestionan actualmente los scripts postinstall. Se considera terminado cuando se deshabilita la ejecución automática amplia de postinstall, se invocan únicamente los paquetes conocidos necesarios y se añade cobertura para detectar dependencias postinstall ausentes.

Escrito por el modelo de indexación a partir del texto del issue.