Improve API /public/v2/api/service-headers to filter services depending on user role

Need to update the API - "/public/v2/api/service-headers" introduce in RANGER-4533 with below :

1. The API should be accessible for non-admin users as well. @PreAuthrize annotation can be removed.
2. Filtering of services depending on user role like done for existing API - "/plugins/services"

cc dineshkumar-yadav / Dhaval.Rajpara