Bi-directional communication using `request-crypto`

`request-crypto` was written with the specific goal of allowing an untrusted user's browser to send data from the Kibana server to the centralized telemetry service and ensure that only the telemetry service can decrypt it.

[Pulse](https://github.com/elastic/kibana/pull/57108/files), the next generation of telemetry, would like to allow the pulse service to send information to the Kibana server and ensure that the data came from the pulse service and can only be read by the Kibana server.