Do not assume packet payload to be a valid UTF-8 string

[romac]

Summary of Bug

Hermers currently assumes that the ICS-04 packet data is valid UTF-8, as it relies on the deprecated packet_data attribute when reconstructing a packet.

Relying on the packet_data attribute enforces a UTF-8 encoded payload (eg. JSON), disallowing Protobuf-encoded payloads which we are starting to see in the wild.

The packet_data atttribute [has been deprecated][0] in favor of packet_data_hex since IBC-Go v1.0.0.

Instead we should use packet_data_hex which is a hex-encoded string.

Version

master

Steps to Reproduce

Sending a packet with a Protobuf-encoded payload results in this error when Hermes attempts to relay it:

WARN ThreadId(222) worker.batch{chain=bbn-test-a}:supervisor.handle_batch{chain=bbn-test-a}:supervisor.process_batch{chain=bbn-test-a}:worker.packet.cmd{src_chain=bbn-test-a src_port=zoneconcierge src_channel=channel-0 dst_chain=bbn-test-b}: task encountered ignorable error: link error: link failed with underlying error: gRPC call `send_tx_simulate` failed with status: status: Internal, message: "failed to decode Protobuf message: EventAttribute.value: Event.attributes: Result.events: SimulateResponse.result: invalid string value: data is not UTF-8 encoded", details: [], metadata: MetadataMap { headers: {"content-type": "application/grpc", "x-cosmos-block-height": "63"} }

Acceptance Criteria

Hermes can relay packets with Protobuf-encoded payloads.

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