Report a warning/error when multiple instance of `@angular/core` are bundled.

[JeanMeche]

Command

build

Description

When the CLI bundles Angular apps it can happen that multiple instances of @angular/core are bundled.

This leads to a variety of errors at runtime that are difficult to diagnose for developers.

Currently on the FW repo we point users toward : angular/angular#35586

Describe the solution you'd like

I'd be great if the CLI could throw a warning/error when it happens so users are aware even before runtime that there is an issue with their bundle and they should have a look at their dependency resolution !