Add detailed Soroban resource fee info in txmeta (#176)

Stellar-ledger.x

@@ -400,10 +400,52 @@ struct DiagnosticEvent
     ContractEvent event;
 };
 
-struct SorobanTransactionMeta 
+struct SorobanTransactionMetaExtV1
 {
     ExtensionPoint ext;
 
+    // The following are the components of the overall Soroban resource fee
+    // charged for the transaction.
+    // The following relation holds:
+    // `resourceFeeCharged = totalNonRefundableResourceFeeCharged + totalRefundableResourceFeeCharged`
+    // where `resourceFeeCharged` is the overall fee charged for the 
+    // transaction. Also, `resourceFeeCharged` <= `sorobanData.resourceFee` 
+    // i.e.we never charge more than the declared resource fee.
+    // The inclusion fee for charged the Soroban transaction can be found using 
+    // the following equation:
+    // `result.feeCharged = resourceFeeCharged + inclusionFeeCharged`.
+
+    // Total amount (in stroops) that has been charged for non-refundable
+    // Soroban resources.
+    // Non-refundable resources are charged based on the usage declared in
+    // the transaction envelope (such as `instructions`, `readBytes` etc.) and 
+    // is charged regardless of the success of the transaction.
+    int64 totalNonRefundableResourceFeeCharged;
+    // Total amount (in stroops) that has been charged for refundable
+    // Soroban resource fees.
+    // Currently this comprises the rent fee (`rentFeeCharged`) and the
+    // fee for the events and return value.
+    // Refundable resources are charged based on the actual resources usage.
+    // Since currently refundable resources are only used for the successful
+    // transactions, this will be `0` for failed transactions.
+    int64 totalRefundableResourceFeeCharged;
+    // Amount (in stroops) that has been charged for rent.
+    // This is a part of `totalNonRefundableResourceFeeCharged`.
+    int64 rentFeeCharged;
+};
+
+union SorobanTransactionMetaExt switch (int v)
+{
+case 0:
+    void;
+case 1:
+    SorobanTransactionMetaExtV1 v1;
+};
+
+struct SorobanTransactionMeta 
+{
+    SorobanTransactionMetaExt ext;
+
     ContractEvent events<>;             // custom events populated by the
                                         // contracts themselves.
     SCVal returnValue;                  // return value of the host fn invocation