Upgrade solidity version in tests to 0.8.x (#843)

Author: cgewecke

package.json

@@ -54,10 +54,10 @@
     "ethereum-waffle": "^3.4.0",
     "ethers": "^5.5.3",
     "ganache-cli": "6.12.2",
-    "hardhat": "^2.17.3",
+    "hardhat": "^2.19.5",
     "hardhat-gas-reporter": "^1.0.1",
     "nyc": "^14.1.1",
-    "solc": "^0.7.5"
+    "solc": "0.8.24"
   },
   "peerDependencies": {
     "hardhat": "^2.11.0"

test/sources/generic/assets/SimpleError.sol

@@ -1,5 +1,5 @@
 // This contract should throw a parse error in instrumentSolidity.js
-pragma solidity ^0.7.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 contract SimpleError {
     uint x = 0;

test/sources/projects/contract-subfolders/contracts/A/ContractA2.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.7.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 import "./../B/ContractB2.sol";
 

test/sources/projects/contract-subfolders/contracts/B/ContractB2.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.7.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 
 contract ContractB {

test/sources/projects/contract-subfolders/hardhat.config.js

@@ -8,7 +8,7 @@ module.exports={
     }
   },
   solidity: {
-    version: "0.7.3"
+    version: "0.8.17"
   },
   paths: {
     sources: './contracts/A'

test/sources/projects/ganache-solcoverjs/contracts/ContractA.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.7.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 
 contract ContractA {

test/sources/projects/ganache-solcoverjs/contracts/ContractB.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.7.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 
 contract ContractB {

test/sources/projects/ganache-solcoverjs/contracts/ContractC.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.7.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 
 contract ContractC {

test/sources/projects/ganache-solcoverjs/hardhat.config.js

@@ -3,7 +3,7 @@ require(__dirname + "/../plugins/nomiclabs.plugin");
 
 module.exports = {
   solidity: {
-    version: "0.7.3"
+    version: "0.8.17"
   },
   networks: {
     coverage: {

test/sources/projects/hardhat-gas-reporter/contracts/ContractA.sol

@@ -1,4 +1,4 @@
-pragma solidity ^0.7.0;
+pragma solidity >=0.8.0 <0.9.0;
 
 
 contract ContractA {