This change adds support for enable and disable user APIs to the high
level rest client. There is a common request base class for both
requests with specific requests that simplify the use of these APIs.
The response for these APIs is simply an empty object so a new response
class has been created for cases where we expect an empty response to
be returned.
Finally, the put user documentation has been moved to the proper
location that is not within an x-pack sub directory and the document
tags no longer contain x-pack.
See #29827
Jay Modi