Node endpoints (#1778)

## Issue Addressed

`node` endpoints in #1434

## Proposed Changes

Implement these:
```
 /eth/v1/node/health
 /eth/v1/node/peers/{peer_id}
 /eth/v1/node/peers
```
- Add an `Option<Enr>` to `PeerInfo`
- Finish implementation of `/eth/v1/node/identity`

## Additional Info
- should update the `peers` endpoints when #1764 is resolved



Co-authored-by: realbigsean <seananderson33@gmail.com>

Cargo.lock

@@ -2455,6 +2455,7 @@ name = "http_api"
 version = "0.1.0"
 dependencies = [
  "beacon_chain",
+ "bs58",
  "discv5",
  "environment",
  "eth1",