Change available errata displayed for content view erratum filter rule to use URL paramater
Refactoring for scoped search
Related to http://projects.theforeman.org/issues/8695 where package group filter rule, package filter rules, and errata filter rules will all be converted to scoped search, since they share the same controller
The errata displayed is under "add" tab for any errata filter on a content view. It needs to be refactored to use a URL parameter like available_for_content_view_filter=errata, that way all of the errata being shown is done through the index of the repository_db_content_controller. When passed with the URL parameter the errata returned will be the errata still available to be added to a content view errata filter. Also the UI has to be changed to take this new URL parameter.
Fixes #10824 - Refactoring errata index to show available errata using a url parameter.
This is part of the conversion to scoped search for the filter_rules. By using a url parameter, the available errata is shown using the index of errata, which will make scoped search easier to implement.