Split common crates out into their own repos (#3890)

## Proposed Changes

Split out several crates which now exist in separate repos under `sigp`.

- [`ssz` and `ssz_derive`](https://github.com/sigp/ethereum_ssz)
- [`tree_hash` and `tree_hash_derive`](https://github.com/sigp/tree_hash)
- [`ethereum_hashing`](https://github.com/sigp/ethereum_hashing)
- [`ethereum_serde_utils`](https://github.com/sigp/ethereum_serde_utils)
- [`ssz_types`](https://github.com/sigp/ssz_types)

For the published crates see: https://crates.io/teams/github:sigp:crates-io?sort=recent-updates.

## Additional Info

- [x] Need to work out how to handle versioning. I was hoping to do 1.0 versions of several crates, but if they depend on `ethereum-types 0.x` that is not going to work. EDIT: decided to go with 0.5.x versions.
- [x] Need to port several changes from `tree-states`, `capella`, `eip4844` branches to the external repos.

validator_client/src/http_api/create_validator.rs

@@ -159,7 +159,7 @@ pub async fn create_validators_mnemonic<P: AsRef<Path>, T: 'static + SlotClock,
             gas_limit: request.gas_limit,
             builder_proposals: request.builder_proposals,
             voting_pubkey,
-            eth1_deposit_tx_data: eth2_serde_utils::hex::encode(&eth1_deposit_data.rlp),
+            eth1_deposit_tx_data: serde_utils::hex::encode(&eth1_deposit_data.rlp),
             deposit_gwei: request.deposit_gwei,
         });
     }