Forum form helpers omit moderators and mishandle dropdowns

[johnjamesjacoby]

Three defects in forum form template helpers are present in 2.6.19:

1. bbp_get_form_forum_moderators() resolves assigned moderator IDs to nicename strings, then tries to pluck user_nicename from those strings. The edit field is blank even when moderators are assigned.
2. The new-forum type dropdown selects the public post status (publish), which is not one of its forum or category options. No option is explicitly selected.
3. The visibility dropdown applies bbp_get_form_forum_type_dropdown instead of a visibility-specific filter. Callbacks on bbp_get_form_forum_visibility_dropdown never run.

Show assigned moderator nicenames when editing, explicitly select forum for a new forum, and add a distinct visibility filter while preserving the existing type-filter call for compatibility. Cover these paths with PHPUnit regression tests. Fix on trunk and backport the narrow source changes and regressions to branches/2.6 for 2.6.20. The broader forum-template coverage remains tracked in #3695.

[johnjamesjacoby]

In 7772:

Forums: Correct form moderator and dropdown values.

Restore assigned moderator nicenames in forum edit forms, explicitly select the forum type for new forums, and add a visibility dropdown filter. Preserve the existing type dropdown filter call for compatibility. Complete the forum-form template tests and add regressions for these defects.

In trunk, for 2.7.

See #3697.
See #3695.

[johnjamesjacoby]

In 7773:

Forums: Backport forum form helper corrections.

Restore assigned moderator nicenames, select the forum type for new forums, and add the visibility dropdown filter while preserving the existing type-filter call. Add targeted regression tests without backporting the broader 2.7 coverage.

In branches/2.6, for 2.6.20.

Fixes #3697.