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/execution_layer/Cargo.toml

@@ -12,7 +12,6 @@ arc-swap = "1.6.0"
 builder_client = { path = "../builder_client" }
 bytes = { workspace = true }
 eth2 = { workspace = true }
-eth2_network_config = { workspace = true }
 ethereum_serde_utils = { workspace = true }
 ethereum_ssz = { workspace = true }
 ethers-core = { workspace = true }