Import bug - Message from Capitalized package is mistaken for Nested Type

The compiler does not distinguish the following two cases:

```protobuf
package somepackage.Core;

message Message {}
```

```protobuf
package somepackage;

message Core {
message Message {}
}
```

as they are both:

```
somepackage.Core.Message
```

Protoc (as far as I've been able to figure out) reports the full type name, but not which part of that is the package, and which is the real type (`somepackage.Core: Message` vs `somepackage: Core.Message`).

In 99% of cases, this will not be a problem, because if users will follow the Protobuf Style Guide, packages will be `lowercase`, and types `CapitalCamelCase`, and the distinction can be made based on that.

https://developers.google.com/protocol-buffers/docs/style#packages

> Package name should be in lowercase, and should correspond to the directory hierarchy. e.g., if a file is in my/package/, then the package name should be my.package.

https://developers.google.com/protocol-buffers/docs/style?hl=cs-CZ#message-and-field-names

> Use CamelCase (with an initial capital) for message names – for example, SongServerRequest. Use underscore_separated_names for field names (including oneof field and extension names) – for example, song_name.

Despite these style guides, there may be some users who are using Capitalized packages and for some reason cannot change the packages to lowercase.

Then, these packages will not be imported correctly from depending packages / messages.

Commencez par reproduire les deux exemples de packages/messages protobuf et comparez la manière dont protoc signale leurs noms de type complets lors des imports dépendants. Suivez ensuite le point d’entrée de la résolution des packages et des types imbriqués du compilateur, puis ajoutez une couverture montrant que les deux cas sont importés distinctement sans casser le comportement des packages en minuscules.

Rédigé par le modèle d'indexation à partir du texte de l'issue.