Publish ssz_types (and deps) to crates.io (#468)

* Rename `hashing` crate to `eth2_hashing`

* Add license, desc to eth2_hashing Cargo.toml

* Remove merkle root from eth2 hashing

* Remove old benches folder (zombied from old branch)

* Add docs to eth2_hashing

* Prepare tree_hash for publishing on crates.io

* Update deps to use crates.io instead of paths

* Update all crates to pull ssz from crates.io

* Remove cached_tree_hash, add patches to manifest

* Fix compile error in benches

* Remove unused code

* Fix fake_crypto compile error

eth2/operation_pool/Cargo.toml

@@ -10,7 +10,7 @@ itertools = "0.8"
 parking_lot = "0.7"
 types = { path = "../types" }
 state_processing = { path = "../state_processing" }
-eth2_ssz = { path = "../utils/ssz" }
+eth2_ssz = "0.1"
 eth2_ssz_derive = { path = "../utils/ssz_derive" }
 
 [dev-dependencies]