The Get Users API also returns users form the restricted realm or built-in users,
as we call them in our docs. One can also change the passwords of built-in
users with the Change Password API
* This commit is part of our plan to deprecate and ultimately remove the use of _xpack in the REST APIs.
- REST API docs
- HLRC docs and doc tests
- Handle REST actions with deprecation warnings
- Changed endpoints in rest-api-spec and relevant file names