Observability Overview page shows unusable buttons to read-only users

[jportner]

Kibana version: 7.14.0 and earlier

Describe the bug:

As a read-only user of any observability feature, you can access the Observability Overview page. However, that page shows many options that regular users cannot actually accomplish.

Steps to reproduce:

1. Create a minimal role, grant it only Read access to the Logs feature
2. Create a user and assign it the new role
3. Log in as the new user
4. Navigate to the Observability Overview page
5. Observe several unusable UI elements: "Install Filebeat", "Install Agent", "Install Metricbeat", "Install Heartbeat", "Install RUM Agent", "Create rule".

Expected behavior:

UI elements should be hidden or grayed out with an appropriate tooltip if the user does not have the required privileges to use that workflow.

Screenshots (if relevant):

Screenshot 1:

Screenshot 2:

Additional context

1. It looks like the "Install X" buttons are all derived from the Home app. I opened a separate issue for that: [Home] Home app shows unusable controls to under-privileged users #106569
2. "Install Agent" and "Install RUM Agent" both end directing the user to the APM app, so those should require APM access?
3. "Install Heartbeat" ends with directing the user to the Uptime app, so that should require Uptime access?
4. There are several 403 errors in the network tab when viewing this page as a read-only user (see Screenshot 2 above)