Remove vendored hashing_serializer and patch it with upstream fix

Cargo.toml

@@ -7,3 +7,4 @@ resolver = "2"
 # TODO(dp): remove before merging
 [patch.crates-io]
 bip32 = { git = "https://github.com/dvdplm/crates/", branch = "dp-fresh-bip32-dependencies" }
+hashing-serializer = { git = "https://github.com/dvdplm/hashing-serializer", branch = "dp-update-deps" }

synedrion/Cargo.toml

@@ -19,7 +19,7 @@ digest = { version = "0.11.0-pre.9", default-features = false, features = ["allo
 hex = { version = "0.4", default-features = false, features = ["alloc"] }
 base64 = { version = "0.22.1", default-features = false, features = ["alloc"] }
 # TODO(dp): Make a PR to update this crate and remove the vendorized copy
-# hashing-serializer = { version = "0.1", default-features = false }
+hashing-serializer = { version = "0.1", default-features = false }
 secrecy = { version = "0.8", default-features = false, features = ["alloc", "serde"] }
 zeroize = { version = "1.8", default-features = false, features = ["alloc", "zeroize_derive"] }
 bip32 = { version = "0.5.2", default-features = false, features = ["alloc", "secp256k1", "k256"] }

synedrion/src/tools/hashing.rs

@@ -3,12 +3,9 @@ use serde::{Deserialize, Serialize};
 use sha2::Sha256;
 use sha3::{Shake256, Shake256Reader};
 
+use hashing_serializer::HashingSerializer;
+
 use crate::curve::Scalar;
-// TODO(dp): the `hashing_serializer` crate uses an old version of `digest` (v0.10) which conflicts
-// with our `impl Hashable for T`, so as a temporary workaround, copy&paste the whole crate source here...
-// When we get a new release of `digest`, ask for an updated version of `hashing_serializer` and
-// remove our copy in `tools/hashing_serializer.rs`
-use crate::tools::hashing_serializer::HashingSerializer;
 use crate::tools::serde_bytes;
 
 /// A digest object that takes byte slices or decomposable ([`Hashable`]) objects.