Iterate over language registrations: don’t need to use .all()
Split registration and use of Language from LanguageTransform

- LanguageRegistration represents a source set type and factory
- LanguageTransform can convert a source set to a ‘TransformationFileType’
- Separate containers for LanguageRegistration and LanguageTransform
- Not (yet) using @LanguageType for registering languages
Converted native language plugins to use @LanguageType
Add display names to native language source sets
Converted jvm language plugins to use @LanguageType