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.)
Given the strict pattern-matching in the inliner, this is the only way
to make it not crash when attempting to inline these stubs. Note that
the IR backend does not currently use the inliner's default method stub
handling; the crash only occurs when a module compiled with the non-IR
JVM backend is attempting to call an inline function with default
arguments defined in a module that was compiled with the IR backend.
