Prefer to rename fields from the class, not from the companion, to be
more in line with the old backend's behavior. This has no effect on the
behavior of current tests but removes differences in metadata (since
metadata has information about every property->field mapping) in some of
them
This is needed to get rid of the code that appends "$companion" to
properties moved from companion, because it caused inconsistencies in
the ABI and in JVM signatures stored in the metadata