Show a list of root problems in the host/service detail if it has a problem and is part of a dependency

[nilmerg]

In order to aid users to resolve an incident we want to list all parents, that may be the cause of the problem, in its detail area.

It should look like this:

Notes

• The list may contain objects of type host, service and (new) redundancy group
  • Members of a redundancy group must not be shown, it's the group's detail area which is responsible for this
• Use \Icinga\Module\Icingadb\Model\UnreachableParent to fetch the content
  • Restrictions must be applied as usual
• Each item links to its detail area
  • Redundancy groups have none yet and will get one separately
  • For now, they won't have a link associated with them
• The mockup above includes a link to all 123 items. This is not required and will also be solved separately
  • This means, all items must be shown
• The list should be entirely replaceable by hooks of type ObjectDetailExtensionHook
  • Currently the plugin output is at the top, where it should still be in case there are no root problems
    • It is using position 0 in all details (e.g. in HostDetail). The root problems should use this position instead, and the plugin output be moved to 1