New analysis rule: strict_named_imports

[p554157atch]

While working on a project, dependency injection in Angular Dart was not working.
I spend few 3-4 hours debugging this issue at the end I found that:

dart:html and http package export class Client and they were colliding with each other and DI was not able to provide the right class.

I was developing in a rush and did not pay attention to this.

Many other users were having similar issues:
#1847
#1851
https://stackoverflow.com/questions/57420313/import-darthtml-in-service-got-exception-no-provider-found-for-dynamic

It might be a good idea to add a new rule in the analyzer plugin strict_named_imports, similar to how Golang does its imports with 0 name collisions.

I would like to keep this rule enabled by default on all of my projects so that name collision issues can be avoided.

This is just a suggestion.

[jodinathan]

have been there too.