[Fleet] Kibana Status should be Unavailable when Fleet Setup fails

[kpollich]

Relates to #111858
Blocked by #112095

in #120020, we set up some initial work to wire up Kibana's status API to Fleet Setup status. However, because Fleet relies on EPR existing, it was unwise to tie Kibana's overall status into a potentially flaky process dependent on EPR's availability over the network. This becomes even more of a concern in air-gapped environments.

Once #112095 is complete, Fleet setup won't have this external network dependency on EPR, and all of its necessary packages will be bundled along with the stack. Once we've eliminated that concern, we can more accurately tie Kibana's status into the success/failure of Fleet setup.

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[joshdover]

@kpollich with bundles packages do you think this concern is still relevant? It could still happen if the user preconfigures other packages that aren't bundled but maybe that's a good thing? I think we could at least go to degraded.

[joshdover]

Nevermind you already state we could revisit once bundled packages were done 🚀

I will probably tackle this after #167246