SCP-2924: Fix ExportTx format

[j-mueller]

Update the ExportTx type to match what is expected by the wallet's balanceTx endpoint.

• We need to fix the code that creates UnbalancedTx on our side to include ony script inputs. The wallet can't deal with public key inputs that aren't its own (and it knows all the ones it owns anyway, so we don't need to include them). See SCP-2925 and SCP-2945

Example JSON:

{
    "transaction": {
        "cborHex": "84a6008182582040ecfe83917b4a...90038ffffff820000840100d87980820000f5f6",
        "description": "",
        "type": "Tx AlonzoEra"
    },
    "redeemers": [
        {
            "input": {
                "id": "40ecfe83917b4a7a54503971ac713585d5db67ec83cc289118924c35af687618",
                "index": 2
            },
            "purpose": "spending",
            "data": "d8799fd8799fd8799f1832ffffd8799f5840ee982bdefb27b57d70ca024416d722e254b3b74296d2232b32dad7c64c6c08f0d1aa17cbc474ed9448330e08578ef0b6efd9be46200fd650308c67977700390d5820d57ea5c597d64721cbe98293c76fe068ea0808e0f3fc99dd9cfcf0f194d1d793d8799fd8799f0101ff1b000001739c890038ffffff"
        },
        {
            "purpose": "minting",
            "data": "d87980",
            "policy_id": "2063caa7ec49402a45050172da6d12897ce6c3561bd930a7e7a0cb14"
        }
    ],
    "inputs": [
        {
            "amount": {
                "unit": "lovelace",
                "quantity": 101
            },
            "datum": "ab4a81419b818fcd4adf710299644a5cea7a05304ea2ab3902a2069fbd1dc25c",
            "address": "addr1wx9vvejjzetdhxk827j5jlatpuy0hqt9w6h4u8amtcwq2fcdnltqc",
            "id": "40ecfe83917b4a7a54503971ac713585d5db67ec83cc289118924c35af687618",
            "index": 2,
            "assets": []
        }
    ]
}

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