diff: fix detection of created/deleted envs
- update cue-diff that now reports all deleted/created attributes
- hopefully make the diff code more simple to understand
- simplify test
- for each change returned by cue-diff aggregate them by env/config
- determine config change type and expr dir to use by looking at the config changelog
- determine env change type by looking at the configs change types
For created/deleted envs, we ignore config attributes changes for brivety.