Missing `unscoped` for ActiveRecord compiler

[paholg]

Calling Model.unscoped returns T.untyped. It would be nice to have the compiler return the relation class instead.

[KaanOzkan]

Right now unscoped definition is coming from the gem RBI as it's defined here and it's eventually mixed into ActiveRecord::Base.

I think it can be added to the relations compiler here, it won't return the model but a PrivateRelation object (docs).