[3.x] Remove support for Doctrine Annotations

[GromNaN]

Q	A
Type	improvement
BC Break	yes
Fixed issues	-

Summary

• Remove AnnotationDriver and its configuration
• Remove @Annotation from attribute classes
• Remove annotations from test documents, already replaced by native attributes

[IonBazan]

• We should also update the docs/annotations-reference.md accordingly.
• PHP attributes are still in Annotations namespace - this is something we won't be able to change easily and might be confusing to new users as docs and other places still use annotations/attributes interchangeably.

[mickverm]

• We should also update the docs/annotations-reference.md accordingly.
• PHP attributes are still in Annotations namespace - this is something we won't be able to change easily and might be confusing to new users as docs and other places still use annotations/attributes interchangeably.

What about using the Annotation namespace as an alias of the Attribute namespace, like Symfony did? And deprecating the annotation namespace later?

https://github.com/symfony/symfony/blob/a518bc2c1a6cf59b65169dadcbeb8f3b91e2c06c/src/Symfony/Component/Routing/Annotation/Route.php

[IonBazan]

@mickverm this is possible, even without aliasing - using inheritance but we would need to keep a copy of all Attribute classes. That should target 2.16.x or 2.17.x then once we decide whether we should pursue that option for v3.
We also need a Rector set to automate the renaming.

[GromNaN]

We have to check if that's possible with attributes, because they are read without actually loading the classes.
I would do the same as the namespace migration of Twig: add aliases in the attributes namespace in 2.x and move the concrete classes to the Attribute namespace in 3.0, keeping aliases in the Annotations namespace as deprecated.

[GromNaN]

See #2933