Improve error message for project-specific `ng` commands outside a project

[dgp1130]

Spin off from #23470.

Project-specific Angular CLI commands don't currently give a great error message when run in a workspace but outside a project. I forget the exact text but something along the lines of "No project available". We should improve this to clarify what we mean by project and ideally list out available projects in the workspace. Something like:

$ ng serve
This is a monorepository workspace and there are many projects you can serve. Run `ng serve <project>` to serve a specific application. Available projects are:
* my-app
* my-lib
* my-other-lib

In really big workspaces we might want to limit this list so we don't explode the console. Maybe limit to 5 or 10 projects with a suggestion to look at angular.json for more.