[K2] Documentation on extension properties is not propagated to the generated extension getters

[vmishenev]

From Google:

If you create val FooClass.extensionProperty with /** docs for extensionProperty */, those docs will never appear for Java consumers. Java consumers never use (and don't get documented) extensionProperty, they only can use FooClassKt.getExtensionProperty(FooClass), which is an autogenerated getter for extensionProperty. With the K1 backend, dackka is putting /** docs for extensionProperty */ on getExtensionProperty, with the K2 backend there are no docs for getExtensionProperty, which means the documentation for extensionProperty is never surfaced for java consumers.

Kotlin K2 IDE plugin (which uses AA) works fine in this case and shows documentation correctly