chore: Deserialize data field of broadcast tx response as hex bytes

[melekes]

Port-of: cometbft/tendermint-rs#1501

Closes #62

[Copilot]

Pull Request Overview

This PR updates the data field for broadcast transaction responses to be deserialized as raw hex bytes rather than base64 strings.

• Test fixtures for v0.34 and v0.38 now include a sample hex-encoded data value.
• Test assertions have been updated to decode and compare the new hex data.
• The serde serializer on tx_sync and tx_async responses was switched to hexstring, and the hexstring deserializer was generalized to any From<Vec<u8>> type.
• A changelog entry documents the bug fix.

Reviewed Changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
rpc/tests/kvstore_fixtures/v0_38/incoming/broadcast_tx_sync.json	Updated data fixture to a hex string
rpc/tests/kvstore_fixtures/v0_38/incoming/broadcast_tx_async.json	Updated data fixture to a hex string
rpc/tests/kvstore_fixtures/v0_38.rs	Added assert_eq decoding hex for data in both sync and async tests
rpc/tests/kvstore_fixtures/v0_34/incoming/broadcast_tx_sync.json	Updated data fixture to a hex string
rpc/tests/kvstore_fixtures/v0_34/incoming/broadcast_tx_async.json	Updated data fixture to a hex string
rpc/tests/kvstore_fixtures/v0_34.rs	Added assert_eq decoding hex and inline comments
rpc/src/endpoint/broadcast/tx_sync.rs	Changed serde data field to use hexstring serializer
rpc/src/endpoint/broadcast/tx_async.rs	Changed serde data field to use hexstring serializer
proto/src/serializers/bytes.rs	Expanded hexstring deserializer to generic T
.changelog/unreleased/bug-fixes/62-result-broadcast.md	Added bug-fix description

Comments suppressed due to low confidence (1)

proto/src/serializers/bytes.rs:10

• The doc comment is now misleading since the function returns a generic T: From<Vec<u8>> instead of specifically Vec<u8>. Consider updating the comment to reflect the return type flexibility.

/// Deserialize a hex-encoded string into `Vec<u8>`