[BUG] Make CatShardsAction internal

[SwethaGuptha]

Describe the bug

With introduction of CatShardsAction, the _cat/shard call requires extra cluster permission cluster:monitor/shards for a non-admin user to call the API which was not required for versions prior to 2.17. We need to fix this to retain the old behaviour

(failed -{"root_cause":[{"type":"security_exception","reason":"no permissions for [cluster:monitor/shards] and User [name=regular, backend_roles=[], requestedTenant=null]"}],"type":"security_exception","reason":"no permissions for [cluster:monitor/shards] and User [name=regular, backend_roles=[], requestedTenant=null]"},"status":403}'})

Related component

Cluster Manager

To Reproduce

Make a _cat/shards call for a non-admin user on 2.17.

Expected behavior

The API call should work without providing user permission for cluster:monitor/shards

Additional Details

Impact: Opensearch versions 2.17 and above.