Improve Efficiency of Kupo UTxO Query by Directly Querying Unspent UTxOs

[bhatt-deep]

Is your feature request related to a problem? Please describe.
Yes, the current implementation of the _utxos_kupo method in the library is inefficient, as it retrieves all UTxOs and then filters for unspent ones. This can be slow and resource-intensive, especially when working with a large number of UTxOs.

Describe the solution you'd like
I propose updating the _utxos_kupo method to directly query unspent UTxOs using the ?unspent flag in the endpoint. This would allow the library to retrieve only the unspent UTxOs, improving the efficiency and performance of the query.

Describe alternatives you've considered
NA

Additional context
NA

[henryyuanheng-wang]

Thanks for flagging this out! Looks like a flag introduced in the recent release. We'll incorporate it into the method.