feat: add paginated packet commitments query to channel/v2

[damiannolan]

Description

Adds paginated queries for packet commitments in channel/v2.

This will be needed for relayers who will also want to query unreceived packets as packets sent must be first queried for their commitments on a source.

ref: #7478

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[damiannolan]

This must be handled different to in v1 as we encode the sequence as big endian bytes when storing commitments.

If parsing the keypart as big endian uint64 fails then it will return 0 - an invalid packet sequence, and is the result of corrupted state.

[sonarcloud]

Quality Gate failed for 'ibc-go'

Failed conditions
64.7% Coverage on New Code (required ≥ 80%)

See analysis details on SonarCloud

[DimitrisJim]

will take on review and merge while Damian's on holiday (and if any nit pops up will push)