Improve typing of classes decorated with definitions

[bartfeenstra]

PluginDefinition and DataDefinition both decorate classes, but require those classes to be aware of their decorators to type on them in their plugin() and data() methods.

Can we do this automatically by having the decorators return a new class which subclasses Plugin and HasData/Data automatically, and types its return value as an intersection?

Blocked by

• Add proper support for class decorators astral-sh/ty#143