[Data Discovery] Confirm correct API access for v9

[davismcphee]

Access to internal APIs will be restricted by default in v9 as detailed in #186781. We need to confirm that our APIs have the intended access configuration (and plan to make adjustments if needed), especially in cases where:

• path: "/api/foo...", access: internal
• path: "/internal/bar..." and access: public

The list of Data Discovery APIs that have public routes prefixed with /internal/ can be found in #186781.

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[mattkime]

Confirmed that routes that are internal are properly set to access: internal