Remove arbitrary-fuzz (#8936)

We have duplicated features which enable `arbitrary` throughout the codebase. These are `arbitrary` and `arbitrary-fuzz`. I think historically these were supposed to be distinct however in practice these function identically and so we can unify them into a single feature to avoid confusion.


Co-Authored-By: Mac L <mjladson@pm.me>

consensus/state_processing/Cargo.toml

@@ -7,10 +7,10 @@ edition = { workspace = true }
 [features]
 default = []
 fake_crypto = ["bls/fake_crypto"]
-arbitrary-fuzz = [
+arbitrary = [
     "dep:arbitrary",
     "smallvec/arbitrary",
-    "types/arbitrary-fuzz",
+    "types/arbitrary",
     "merkle_proof/arbitrary",
     "ethereum_ssz/arbitrary",
     "ssz_types/arbitrary",