We are going to deprecate `WITH_RUNTIME` directive. The main reason
behind this change is that `WITH_STDLIB` directive better describes
its meaning, specifically it will add kotlin stdlib to test's classpath.
The first change here is swapping the isCompatibility and hasJvmDefault
checks. Otherwise behavior could be different depending on -Xjvm-default
mode even for non-JvmDefault declarations, which makes little sense.
Another change is avoiding generating $default stubs for fake overrides
in interfaces, which replicates the behavior of the current backend.
(Note that this change also fixes the first problem on the newly added
tests, but the first change seems useful anyway.)
Ivan Kylchik