Make params store readable so the batch state map mirror can be removed

[notJoon]

Suggested by @benluelo (Union team) when reporting the batch packets state map keying bug (fixed in #42).

Currently commit() (r/core/ibc/v1/core) writes commitments via params.SetBytes(hex(key), value), but the chain/params stdlib package (gno, gnovm/stdlibs/chain/params/params.gno) exposes no reader. As a result, r/core/ibc/v1/core/state.gno keeps an in-memory batchPackets / batchReceipts mirror just so relayers have something to query. The mirror duplicates the params store and must be kept consistent with it on every write/delete.

If the stdlib gains a params.GetBytes(key) ([]byte, bool) (or equivalent), the mirror maps can be deleted entirely, and QueryBatchPackets / QueryBatchReceipts (plus other Query* helpers) can read directly from params.

Scope

• Upstream: add the reader API to chain/params in gno.
• This repo: once available, drop State.batchPackets / State.batchReceipts, remove the mirror writes in saveBatchPackets / setBatchPackets / saveBatchReceipts / deletePacketCommitment / deletePacketReceipt, and re-point reads (getBatchPackets / getBatchReceipts / hasPacketCommitment / hasAcknowledgement / hasPacketReceipt / acknowledgementHash / Query*) at the new accessor.

Out of scope

• Client / connection / channel state maps: those are keyed by small IDs and accessed only via dedicated Query* functions; removing them is a separate decision.

[notJoon]

considered applying this feature directly to the vendor dependency, but since it could introduce issues related to #51 and there was also a possibility that the final implementation might diverge from the pre-applied version, so I choose to submit the PR to the Gno repo first.

If it gets merged we should proceed the follow-up work alongside a vendored dependency update.