[FEATURE] Add new REST admin API edpoint

Is your feature request related to a problem?
Add a new REST admin endpoint to update the configuration of multiple configuration types.
Such endpoint will be helpful to update internal users, roles, roles mapping in one request

What solution would you like?
Endpoint:
PATCH _plugins/_security/api/configuration/update

Payload:

{
  "actiongroups": [ 
      {
       "op": "add", "path": "/CREATE_INDEX", 
       "value": { "allowed_actions": ["indices:admin/create", "indices:admin/mapping/put"] }
      }], 
   "nodes_dn": [...], 
   "internalusers": [...]
 }

in other words the endpoint will combine exiting patch endpoints and update the index via bulk.

Start by reading the existing patch endpoints, which the issue says this endpoint should combine, and trace the PATCH _plugins/_security/api/configuration/update entry point. Define completion as one request updating actiongroups, nodes_dn, and internalusers through the proposed bulk index update. No files or tests are named, so the implementation locations and validation approach must first be established.