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.

beacon_node/genesis/Cargo.toml

@@ -16,9 +16,9 @@ eth1 = { path = "../eth1"}
 rayon = "1.4.1"
 state_processing = { path = "../../consensus/state_processing" }
 merkle_proof = { path = "../../consensus/merkle_proof" }
-eth2_ssz = "0.4.1"
-eth2_hashing = "0.3.0"
-tree_hash = "0.4.1"
+ethereum_ssz = "0.5.0"
+ethereum_hashing = "1.0.0-beta.2"
+tree_hash = "0.5.0"
 tokio = { version = "1.14.0", features = ["full"] }
 slog = "2.5.2"
 int_to_bytes = { path = "../../consensus/int_to_bytes" }