Interfaces's extensions not generated

[Ivan Sablin]

Extensions not generated for interfaces and interface's implementations.
https://github.com/Merseyside/mersey-kmp-time/blob/master/time/src/commonMain/kotlin/com/merseyside/merseyLib/time/ext/ZonedTimeUnitExt.kt (generates as expected in extensions swift block because ZonedTimeUnit doesn't extend any interface)
https://github.com/Merseyside/mersey-kmp-time/blob/master/time/src/commonMain/kotlin/com/merseyside/merseyLib/time/ext/TimeUnitExt.kt (generates separately with class name of kotlin file contains extensions)

Example of usage: https://github.com/Merseyside/mersey-kmp-time/blob/master/ios-app-swiftui/ios-app-swiftui/TimeTest.swift

[Sven Bendel]

Same for sealed classes.