Implement Compact in Key-value API

[marcosflobo]

Is your feature request related to a problem? Please describe.
No, it's not

Describe the solution you'd like
Implement the Compact service from the Key-value API offered by jetcd client https://github.com/etcd-io/jetcd/blob/master/jetcd-core/src/main/java/io/etcd/jetcd/KVImpl.java

Compact compacts the event history in the etcd key-value store. The key-value store should be periodically compacted or the event history will continue to grow indefinitely.

Describe alternatives you've considered
No alternatives, since it's required for 1.0.0

Additional context
No