Better support `ng new` use cases

Start by reviewing the existing ng new and ng generate behavior and the linked Angular workspace file-structure documentation. Compare the current --create-application=false flow with the requested application, library, and multi-app use cases. Done requires an agreed direction for workspace terminology and command boundaries before implementation.

🚀 Feature request

/cc @mgechev

Command (mark with an x)

• new
• generate

Description

We should rethink some of the DX around ng new, as it was originally intended to make new Angular applications, but has expanded somewhat, particularly with monorepos. There are three things in particular which are a bit awkward:

1. There is no way to create an Angular library (using the CLI) without using a monorepo structure. This may not be desired and makes library authorship a little more awkward.
2. To use a monorepo structure, users are supposed to use ng new --create-application=false, which is a pretty awkward syntax and doesn't make clear that this is intended for a monorepo/multi-app workspace.
3. Reevaluate the definition of "workspace". I can't speak for others, but I always interpreted a "workspace" as effectively a monorepository for Angular apps. Looking through docs, it seems that anything with an angular.json file is technically a "workspace", so ng new technically creates a workspace, even though it isn't a monorepo. I think this definition of "workspace" only really applies internally so we should think more critically about the language here.

Additional context: https://twitter.com/justinfagnani/status/1373336274384293889

Describe the solution you'd like

I'm thinking we could add an extra flag to ng new to decide whether to make a standalone application (ng new --type app), a multi-app workspace (ng new --type workspace, equivalent to today's ng new --create-application=false), or a standalone library (ng new --type library). Note that ng new --type app and ng new --type library both technically create a "workspace" per the above definition. We might want to either tweak the definition of "workspace" to mean "a multi-app Angular repo" or use something like ng new --type empty-workspace.

This would be distinguished from ng generate because ng new makes a new repository while ng generate works within an existing repository. Arguably we should merge ng new and ng generate (maybe inferring from file path context whether a new repository is required).

Some of the broader questions we should discuss:

1. How should we position Angular "workspaces"? Are they for monorepositories or not?
2. How should ng new and ng generate work together or be merged?

Describe alternatives you've considered

Apparently you can use ng-packagr to generate a library without a workspace, but you're losing a lot of the benefits of the CLI by doing so: https://twitter.com/Splaktar/status/1373373386802479105