## Description 

Add the minimum network traits. In the beginning, implementations of the
traits will just wrap anemo unicast RPCs. Later, streaming and
connection management logic can be added inside `NetworkClient` and
`NetworkServer` implementations.

## Test Plan 

n/a

---
If your changes are not user-facing and do not break anything, you can
skip the following section. Otherwise, please briefly describe what has
changed under the Release Notes section.

### Type of Change (Check all that apply)

- [ ] protocol change
- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes