Deprecate specialized unsigned iterators for removal.
Fix compiler tests:
- drop unsignedLiteralsOn1_2 because apiVersion 1.2 is no longer supported
- drop experimental unsigned literals diagnostic test
- Setting -Doverwrite.output=true updates gold data
- Big packages don't get split into chunks
- Unique lines in the API are marked with /*∆*/ and diff test is removed
- Annotations on separate lines and other dump format tweaks
- Test data moved to libraries/stdlib/api/
- Minor visibility fix to Enum members
Abduqodiri Qurbonzoda