Reduce the size of packet acknowledgement queries

[seanchen1991]

Summary

#3334 uncovered an issue where query_packet_acknowledgements returns too much data such that it surpasses the 4MB message decoding limit imposed by the dependency on tonic.

#3335 addressed this by increasing the message decoding limit (and also making it configurable). However, this doesn't address the root cause of the issue, which is that this query shouldn't return this much data in the first place.

The query_packet_acknowledgements query asks the chain to fetch acknowledgements for all sequences in the packet_commitment_sequences list. However, if this list is empty when the query is made, i.e., there is nothing to be relayed, the query returns all packet acknowledgements for the given channel, hence why the query sometimes returns too much data.

Acceptance Criteria

To address the root cause of this issue, the query_packet_acknowledgements query should not return any acknowledgements when the packet_commitment_sequences list is empty. We should also be able to revert the message decoding limit to 4MB, though we should perhaps keep this value configurable.

• Change query_packet_acknowledgements query should not return any acknowledgements when the packet_commitment_sequences list is empty
• Revert the message decoding limit back to 4MB

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