When configuring a repository or a default reviewer, the selectors for

review groups and repositories would only show visible items. This meant

that if a company was making groups invisible to keep others from seeing

them, but not to phase them out, then they wouldn't have the ability to

specify them when configuring repositories or default reviewers.
This worked back in Review Board 3, but regressed in 4 with the addition

of the related object selectors. The reason this happened is that we

moved from fetching all possible items at page render time to querying

via the API, and the review groups API lacked any way to query

non-visible review groups.
Now that the API is gaining this support, we can redo these widgets.

They now take options for showing non-visible items, and will funnel the

correct state down to the JavaScript for inclusion in the API call.
This is enabled by default, in order to ensure users who make heavy use

of hidden review groups/repositories for access control reasons will be

able to configure these. Users interacting with the selector will only

be able to select review groups/repositories they have access to, so

this will be safe.

Unit tests pass.
Successfully added hidden review groups and repositories in the Default

Reviewers page, and added hidden review groups in the Repository page.