Mark classes internal that are internal

[jwage]

There really isn't much that the outside should be depending on in this library/tool so mark everything as @internal that nobody should be depending on.

[stof]

well, I would say that the Tools/Console aprt should not be considered as internal, otherwise DoctrineMigrationsBundle reusing these commands to register them directly in the Symfony CLI would have to be considered as invalid (from the bundle perspective, we need to be able to rely on backward compatibility for these parts in non-major releases, and that means not being internal).
The Configuration part should also be considered public API (even the built-in runner still relies on receiving a configuration)

[jwage]

Yes, the commands, configuration, etc. wouldn't be considered internal.

[stof]

well, the initial description says mark everything as @internal

[jwage]

Updated the description to be more accurate.