Support closing issues as duplicates via --reason duplicate and
--duplicate-of <issue> flags. The --duplicate-of flag accepts an issue
number or URL, validates it references a different issue (not a PR),
and passes the duplicate issue ID to the closeIssue mutation.
Feature detection checks whether the GHES instance supports the
DUPLICATE enum value in IssueClosedStateReason before using it.
This commit expands on @nobe4 initial work by bringing the owner and repository name to the most obvious issue and PR number output use cases before making a second pass for any edge cases.
- `issue close` no longer fetches all issue fields and thus avoids the
problem when loading failed due to token not having access to projects
- `issue close` now accepts either issue or pull number as argument.
