feat(target_chains/ethreum): add transaction fee handling to fee calculations and state management in pyth contract

Author: cctdaniel

target_chains/ethereum/contracts/contracts/pyth/Pyth.sol

@@ -330,7 +330,8 @@ abstract contract Pyth is
     function getTotalFee(
         uint totalNumUpdates
     ) private view returns (uint requiredFee) {
-        return totalNumUpdates * singleUpdateFeeInWei();
+        return
+            (totalNumUpdates * singleUpdateFeeInWei()) + transactionFeeInWei();
     }
 
     function findIndexOfPriceId(

target_chains/ethereum/contracts/contracts/pyth/PythGetters.sol

@@ -91,4 +91,8 @@ contract PythGetters is PythState {
     function governanceDataSourceIndex() public view returns (uint32) {
         return _state.governanceDataSourceIndex;
     }
+
+    function transactionFeeInWei() public view returns (uint) {
+        return _state.transactionFeeInWei;
+    }
 }

target_chains/ethereum/contracts/contracts/pyth/PythSetters.sol

@@ -48,4 +48,8 @@ contract PythSetters is PythState, IPythEvents {
     function setGovernanceDataSourceIndex(uint32 newIndex) internal {
         _state.governanceDataSourceIndex = newIndex;
     }
+
+    function setTransactionFeeInWei(uint fee) internal {
+        _state.transactionFeeInWei = fee;
+    }
 }

target_chains/ethereum/contracts/contracts/pyth/PythState.sol

@@ -38,6 +38,8 @@ contract PythStorage {
         // Mapping of cached price information
         // priceId => PriceInfo
         mapping(bytes32 => PythInternalStructs.PriceInfo) latestPriceInfo;
+        // Fee charged per transaction, in addition to per-update fees
+        uint transactionFeeInWei;
     }
 }