## Summary

Closes elastic#227311

Right now if we create a background search of an unsaved dashboard it
doesn't store the panels/references in the saved object, that menas that
we can't really restore it. With this we store them even if the
dashboard isn't saved but I don't have any context on why it wasn't done
like this before so happy to get input on it.

---

#### Background an unsaved dashboard and just open it again

Before

https://github.com/user-attachments/assets/fd282c28-53ea-49dc-b58b-1441e25dfbb1

After

https://github.com/user-attachments/assets/d39fbef0-d9b2-4763-bd10-1db98b4fc667

---

#### Background an unsaved dashboard, remove it and open it again

Before

https://github.com/user-attachments/assets/9c1ba24d-a55f-4176-a409-5070d282110d

After

https://github.com/user-attachments/assets/7d0a4e3e-e213-40f4-9c41-50783a08b2df

---

### Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

- [ ] [Unit or functional
tests](https://www.elastic.co/guide/en/kibana/master/development-tests.html)
were updated or added to match the most common scenarios
- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
- [x] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.

(cherry picked from commit 9686335)