* Fix newlines in JSON output
This changes the JSON output to be more consistent about where newlines are included. Previously it only included them between lines in a multiline diff. That meant single line changes were treated a bit weirdly. This changes it to append a newline to every line.
When feeding the results into `arc lint` this behaves correctly. I have only done limited testing though, in particular there's a possibility it might not work with files with `\r\n` endings (though that would have been the case before too).
Fixes#4259
* Update tests
# Conflicts:
# tests/writemode/target/output.json
