Migrate from deprecated `@JvmDefault` and `-Xjvm-default=enabled` to `-Xjvm-default=all`

We should move to `-Xjvm-default=all`. Per [docs](https://blog.jetbrains.com/kotlin/2020/07/kotlin-1-4-m3-generating-default-methods-in-interfaces/):

> If you used the @JvmDefault annotation before, you can safely remove it and use one of the new modes. If you already used -Xjvm-default=enable, which generated only the default method implementations, you can now replace it with -Xjvm-default=all.