[Links] Unable to view by-reference links panels if user does not have saved object management permissions

[Heenawter]

Tip

This was reported here: #166896 (comment)

Describe the bug:

When a user does not have Saved Objects Management permissions in their role, they are unable to see by-reference links panels and simply see the following "Forbidden" error:

Looking into this, and it seems to fail at the point we try to fetch the Links saved object from the content management client in the unwrapMethod from src/plugins/links/public/services/attribute_service.ts. Fetching other saved objects (visualizations, dashboards, etc.) do not fail, so I wonder if we have to add something to the Links CM type that will allow this? 🤔

Steps to reproduce:

1. Create a dashboard with one by-reference links panel and another by-value.
2. Create a role without Saved Objects Management permissions.
3. Create a user and assign that role to them.
4. Login to Kibana with this new user.
5. Open the Dashboard from step 1.
6. The by-reference links panel will fail to load 🔥 But the by-value links panel will load fine! 🎉

Note

Note that other by reference panels load just fine without this permission.

Expected behavior:
Links panels should be fetchable without Saved Objects Management permissions, just like other by-reference panels.

[elasticmachine]

Pinging @elastic/kibana-presentation (Team:Presentation)