[Debug] Trigger a deprecation when an @internal class/interface/trait is used #23800
Description
| Q | A |
|---|---|
| Bug report? | no |
| Feature request? | yes |
| BC Break report? | no |
| RFC? | no |
| Symfony version | 3.4 |
We use @internal quite extensively, yet, the DebugClassLoader class doesn't warn when one uses such a tagged class/interface/trait.
We should trigger the same kind of deprecation as we already do for @final, with the added condition that the root namespace needs to be different (don't trigger within the same root namespace.)