decouple eth2 from store and lighthouse_network (#6680)

- #6452 (partially)


  Remove dependencies on `store` and `lighthouse_network`  from `eth2`. This was achieved as follows:

- depend on `enr` and `multiaddr` directly instead of using `lighthouse_network`'s reexports.
- make `lighthouse_network` responsible for converting between API and internal types.
- in two cases, remove complex internal types and use the generic `serde_json::Value` instead - this is not ideal, but should be fine for now, as this affects two internal non-spec endpoints which are meant for debugging, unstable, and subject to change without notice anyway. Inspired by #6679. The alternative is to move all relevant types to `eth2` or `types` instead - what do you think?

beacon_node/beacon_chain/src/attestation_rewards.rs

@@ -1,7 +1,7 @@
 use crate::{BeaconChain, BeaconChainError, BeaconChainTypes};
-use eth2::lighthouse::attestation_rewards::{IdealAttestationRewards, TotalAttestationRewards};
-use eth2::lighthouse::StandardAttestationRewards;
-use eth2::types::ValidatorId;
+use eth2::types::{
+    IdealAttestationRewards, StandardAttestationRewards, TotalAttestationRewards, ValidatorId,
+};
 use safe_arith::SafeArith;
 use serde_utils::quoted_u64::Quoted;
 use state_processing::common::base::{self, SqrtTotalActiveBalance};