Implement eth_call for methods returning struct type (#59)

* Handle tuple return type in ethereum host API

* Update graph-cli version to fix eth_call error

* Handle all types in struct based on abi

Co-authored-by: prathamesh0 <prathamesh.musale0@gmail.com>

packages/graph-node/test/contracts/Example.sol

@@ -5,6 +5,11 @@ pragma solidity ^0.8.0;
 contract Example {
     uint256 private _test;
 
+    struct Bid {
+        uint128 bidAmount1;
+        uint128 bidAmount2;
+    }
+
     event Test(string param1, uint8 param2);
 
     function getMethod() public view virtual returns (string memory)
@@ -12,8 +17,21 @@ contract Example {
         return 'test';
     }
 
+    function addMethod(uint128 bidAmount1, uint128 bidAmount2) public pure returns (uint) {
+        return bidAmount1 + bidAmount2;
+    }
+
+    function structMethod(uint128 bidAmount1, uint128 bidAmount2) public pure returns (Bid memory) {
+        Bid memory bid;
+        bid.bidAmount1 = bidAmount2;
+        bid.bidAmount2 = bidAmount1;
+
+        return bid;
+    }
+
     function emitEvent() public virtual returns (bool) {
         emit Test('abc', 123);
+
         return true;
     }
 }