Make it possible to use `modules` or `packages` configurations with `files`

Feature

Make it possible to use modules or packages configurations with files.

Pitch

Currently, when using modules or packages configurations with files, we get the following error:

usage: mypy [-h] [-v] [-V] [more options; see below]
            [-m MODULE] [-p PACKAGE] [-c PROGRAM_TEXT] [files ...]
mypy: error: May only specify one of: module/package, files, or command.

I did not see any mention of such restriction in the documentation.

Nevertheless, it could be useful to check in a single mypy execution:

• the core packages with modules or packages, which configurations seem to handle correctly pkgutil-style namespace packages (see #9393),
• other standalone scripts (tools, tests, ...) with files.

Commencez par la validation en ligne de commande de mypy qui émet l’erreur module/package, files, or command, puis comparez-la à la documentation de configuration de modules, packages et files. Le travail est terminé lorsqu’une invocation peut vérifier des modules ou des packages configurés avec des fichiers autonomes, avec une couverture du comportement existant des namespace packages.