Support async ErrorStateMatcher

#### Please describe the feature you would like to request.

Currently, `ErrorStateMatcher` doesn't support return type `Promise` and `Observable`. Its return type is only `boolean`.

#### What is the use-case or motivation for this proposal?

I need to show `` when checked `input` is invalid after validation. This validation does need to call HTTP request(async). For example, when ID field in registration form is not unique, i should show `` because registration form doesn't allow to use the input's value as duplicated ID with other user. To provide this feature, `ErrorStateMatcher` has to support return type as `Promise` or `Observable`.

Empieza leyendo la API de ErrorStateMatcher y el flujo de validación existente de mat-error, centrándote en cómo se comprueba la validez de la entrada. Compara los casos solicitados de Promise y Observable y define la finalización de modo que los resultados de la validación asíncrona provoquen de forma fiable el estado mat-error correspondiente para los IDs duplicados.

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