feat: add hardhat plugin to support HTS emulation in fork testing

tools/hardhat-forking-plugin-usage-example/.env.example

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+# For Hedera Testnet
+# The operator private keys start with "0x" and are in hexadecimal format
+# Your testnet account ECDSA hex-encoded private key (Ex: 0xb46751179bc8aa9e129d34463e46cd...)
+TESTNET_OPERATOR_PRIVATE_KEY=''
+
+# For Hedera Previewnet
+# Your previewnet account ECDSA hex-encoded private key (Ex: 0x46751179bc8aa9e129d34463e...)
+PREVIEWNET_OPERATOR_PRIVATE_KEY=""
+
+# For Hedera Mainnet
+# Your mainnet account ECDSA hex-encoded private key (Ex: 0x46751179bc8aa9e129d34463e...)
+MAINNET_OPERATOR_PRIVATE_KEY=""
+
+# For Hedera Local Node
+# The operator private keys start with "0x" and are in hexadecimal format
+# Your Hedera Local Node ECDSA account alias private key (Ex: 0x105d050185ccb907fba04dd92d...)
+LOCAL_NODE_OPERATOR_PRIVATE_KEY=''
+# Your Hedera Local Node JSON-RPC endpoint URL (ex: 'http://localhost:7546/')
+LOCAL_RPC_URL='http://127.0.0.1:8545/'
+
+#  MirrorNode URL - Hedera Token Service data will be retrieved from this URL and used to set up storage
+# for the corresponding token proxies.
+HEDERA_MIRRORNODE_URL=https://testnet.mirrornode.hedera.com/api/v1/

tools/hardhat-forking-plugin-usage-example/.gitignore

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+node_modules
+.env
+coverage
+coverage.json
+typechain
+typechain-types
+
+# Hardhat files
+cache
+artifacts
+
+.vscode

tools/hardhat-forking-plugin-usage-example/README.md

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+# Hashgraph Forking Plugin for HardHat - Usage Example
+
+This example demonstrates how to use the Hedera plugin in the smart contract development process with HardHat.
+
+## Configuration
+
+To begin, you need to start the HardHat fork, which enables the use of the `hardhat_setStorageAt` and `hardhat_setCode` methods:
+
+```bash
+npx hardhat node --fork https://testnet.hashio.io/api
+```
+
+## Running Tests
+
+To execute the tests, first install the necessary dependencies:
+
+```bash
+npm install
+```
+
+Then run the tests with the following command:
+
+```bash
+npx hardhat test
+```

tools/hardhat-forking-plugin-usage-example/contracts/IERC20.sol

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+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+/// https://hips.hedera.com/hip/hip-218
+/// https://hips.hedera.com/hip/hip-376
+interface IERC20 {
+    function name() external view returns (string memory);
+    function symbol() external view returns (string memory);
+    function decimals() external view returns (uint8);
+
+    function totalSupply() external view returns (uint256);
+    function balanceOf(address account) external view returns (uint256);
+    function transfer(address recipient, uint256 amount) external returns (bool);
+
+    function allowance(address owner, address spender) external view returns (uint256);
+    function approve(address spender, uint256 amount) external returns (bool);
+    function transferFrom(address sender, address recipient, uint256 amount) external returns (bool);
+
+    event Transfer(address indexed from, address indexed to, uint256 value);
+    event Approval(address indexed owner, address indexed spender, uint256 value);
+}

tools/hardhat-forking-plugin-usage-example/hardhat.config.js

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+/*-
+ *
+ * Hedera Hardhat Plugin Example Project
+ *
+ * Copyright (C) 2024 Hedera Hashgraph, LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+require("@nomicfoundation/hardhat-toolbox-viem");
+require("@nomicfoundation/hardhat-chai-matchers");
+require("@hashgraph/hardhat-forking-plugin");
+
+// Import dotenv module to access variables stored in the .env file
+require("dotenv").config();
+
+/** @type import('@hashgraph/hardhat-forking-plugin').HeaderaHardhatConfig */
+module.exports = {
+  mocha: {
+    timeout: 3600000
+  },
+  solidity: {
+    version: "0.8.9",
+    settings: {
+      optimizer: {
+        enabled: true,
+        runs: 500
+      }
+    }
+  },
+  // This specifies network configurations used when running Hardhat tasks
+  defaultNetwork: "local",
+  networks: {
+    local: {
+      // Your Hedera Local Node address pulled from the .env file
+      url: process.env.LOCAL_RPC_URL,
+      // Conditionally assign accounts when private key value is present
+      accounts: process.env.LOCAL_NODE_OPERATOR_PRIVATE_KEY ? [process.env.LOCAL_NODE_OPERATOR_PRIVATE_KEY] : []
+    },
+    testnet: {
+      // HashIO testnet endpoint
+      url: 'https://testnet.hashio.io/api',
+      // Conditionally assign accounts when private key value is present
+      accounts: process.env.TESTNET_OPERATOR_PRIVATE_KEY ? [process.env.TESTNET_OPERATOR_PRIVATE_KEY] : []
+    },
+
+    /**
+     * Uncomment the following to add a mainnet network configuration
+     */
+    mainnet: {
+      // HashIO mainnet endpoint
+      url: 'https://mainnet.hashio.io/api',
+      // Conditionally assign accounts when private key value is present
+      accounts: process.env.MAINNET_OPERATOR_PRIVATE_KEY ? [process.env.MAINNET_OPERATOR_PRIVATE_KEY] : []
+    },
+
+    /**
+     * Uncomment the following to add a previewnet network configuration
+     */
+    previewnet: {
+      // HashIO previewnet endpoint
+      url:'https://previewnet.hashio.io/api',
+      // Conditionally assign accounts when private key value is present
+      accounts: process.env.PREVIEWNET_OPERATOR_PRIVATE_KEY ? [process.env.PREVIEWNET_OPERATOR_PRIVATE_KEY] : []
+    }
+  }
+};