Improve exports txs to csv for contract addresses

[tdroxler]

For example when exporting from this address, if we take that transaction as an example, the toAddresses is wrong (empty):

fromAddresses, toAddresses, hintAmount
1BZ5nen4sNEgvGh7LDM7hn7rDkaA7jbzWHpBMT6j89U3G-2A7QeUr9z6qv8ywYX79jtYAnr8BtcYmFMCQ49ctVwL8z3,,,-50

Amount is correct, but the addresses are wrong because we are currently removing the change addresses, to make it nicer when filling taxes . It happens here:

explorer-backend/app/src/main/scala/org/alephium/explorer/api/model/Transaction.scala

Lines 43 to 58 in 35c86ef

	def toCsv(address: Address): String = {
	val dateTime = Instant.ofEpochMilli(timestamp.millis)
	val fromAddresses = UtxoUtil.fromAddresses(inputs)
	val fromAddressesStr = fromAddresses.mkString("-")
	val toAddresses =
	UtxoUtil.toAddressesWithoutChangeAddresses(outputs, fromAddresses).mkString("-")
	val deltaAmount = UtxoUtil.deltaAmountForAddress(address, inputs, outputs)
	val amount = deltaAmount.map(_.toString).getOrElse("")
	val amountHint = deltaAmount
	.map(delta =>
	new java.math.BigDecimal(delta).divide(new java.math.BigDecimal(ALPH.oneAlph.v))
	)
	.map(_.toString)
	.getOrElse("")
	s"${hash.toHexString},${blockHash.toHexString},${timestamp.millis},$dateTime,$fromAddressesStr,$toAddresses,$amount,$amountHint\n"
	}

and here

explorer-backend/app/src/main/scala/org/alephium/explorer/util/UtxoUtil.scala

Lines 61 to 68 in 35c86ef

	def toAddressesWithoutChangeAddresses(
	outputs: ArraySeq[Output],
	changeAddresses: ArraySeq[Address]
	): ArraySeq[Address] = {
	outputs.collect {
	case output if !changeAddresses.contains(output.address) => output.address
	}.distinct
	}

.