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/http_api/src/standard_block_rewards.rs

@@ -2,7 +2,7 @@ use crate::sync_committee_rewards::get_state_before_applying_block;
 use crate::BlockId;
 use crate::ExecutionOptimistic;
 use beacon_chain::{BeaconChain, BeaconChainTypes};
-use eth2::lighthouse::StandardBlockReward;
+use eth2::types::StandardBlockReward;
 use std::sync::Arc;
 use warp_utils::reject::unhandled_error;
 /// The difference between block_rewards and beacon_block_rewards is the later returns block