Connectors cannot call refresh on .elastic-connectors after System Index conversion

[seanstory]

Bug Description

When launching a fresh agentless connector on 9.0.0-SNAPSHOT, I'm hitting:

[elastic_agent.connectors][error] Error while checking existence of connector 'f641ab2c-8002-41d5-959d-943425d217a2': AuthorizationException(403, 'security_exception', 'action [indices:admin/refresh] is unauthorized for API key id [W-SfqJQBlxUzDiujVIuP] of user [elastic/fleet-server] on restricted indices [.elastic-connectors], this action is granted by the index privileges [maintenance,manage,all]')

Jedr suggests that we should be able to remove these refresh checks, since the Connectors APIs are doing these for us under the hood.

To Reproduce

1. Create a 9.0.0 deployment
2. create a Confluence Cloud connector from the integrations tab
3. navigate to the Agent UI
4. click on the Agent and view its connectors logs
5. see the above stack trace

Expected behavior

Connectors should have sufficient privileges do do whatever they try to do, and should only do the things they have privileges for.

Environment

9.0.0-SNAPSHOT

[jedrazb]

Not in scope for Feb 2025 anymore, since we want to migrate to Connector APIs fully