* Add rlp encoding support for IpAddr
* Lock support behind std feature
* Replace Octets with IpAddr
* Derive Rlp traits for NodeEndpoint
* Derive Rlp traits for NodeRecord
* Add serde support to NodeRecord
* Move NodeRecord to primitives
along with NodeKey and Octets
* Reexport NodeRecord from discv4
* Move NodeKey and kad_key back to discv4::node
Also, move NodeRecord::key functionality to a helper function: discv4::node::record_key.
This avoids the discv5 dependency in the primitives crate.
* Fix NodeRecord (de)serializing
The default derive macros work with a dictionary like display.
Changed that to serde_with macros, that use Display and FromStr traits.
* Add some tests for NodeRecord (de)serializing
* Hide NodeKey struct
* Move Octets after NodeRecord
* Replace record_key with From trait
* Fix clippy error
unnecessary into()
