[red-knot] `typing.dataclass_transform` (#17445)
## Summary
* Add initial support for `typing.dataclass_transform`
* Support decorating a function decorator with `@dataclass_transform(…)`
(used by `attrs`, `strawberry`)
* Support decorating a metaclass with `@dataclass_transform(…)` (used by
`pydantic`, but doesn't work yet, because we don't seem to model
`__new__` calls correctly?)
* *No* support yet for decorating base classes with
`@dataclass_transform(…)`. I haven't figured out how this even supposed
to work. And haven't seen it being used.
* Add `strawberry` as an ecosystem project, as it makes heavy use of
`@dataclass_transform`
## Test Plan
New Markdown tests
