Add Blockhash library following EIP-2935 (#5642)

Co-authored-by: Arr00 <13561405+arr00@users.noreply.github.com>

test/utils/Blockhash.test.js

@@ -0,0 +1,76 @@
+const { ethers } = require('hardhat');
+const { expect } = require('chai');
+const { loadFixture, mine, mineUpTo, setCode } = require('@nomicfoundation/hardhat-network-helpers');
+const { impersonate } = require('../helpers/account');
+
+async function fixture() {
+  const mock = await ethers.deployContract('$Blockhash');
+  return { mock };
+}
+
+const HISTORY_STORAGE_ADDRESS = '0x0000F90827F1C53a10cb7A02335B175320002935';
+const SYSTEM_ADDRESS = '0xfffffffffffffffffffffffffffffffffffffffe';
+const HISTORY_SERVE_WINDOW = 8191;
+const BLOCKHASH_SERVE_WINDOW = 256;
+
+describe('Blockhash', function () {
+  before(async function () {
+    Object.assign(this, await loadFixture(fixture));
+
+    impersonate(SYSTEM_ADDRESS);
+    this.systemSigner = await ethers.getSigner(SYSTEM_ADDRESS);
+  });
+
+  it('recent block', async function () {
+    await mine();
+
+    const mostRecentBlock = (await ethers.provider.getBlock('latest')).number;
+    const blockToCheck = mostRecentBlock - 1;
+    const fetchedHash = (await ethers.provider.getBlock(blockToCheck)).hash;
+    await expect(this.mock.$blockHash(blockToCheck)).to.eventually.equal(fetchedHash);
+  });
+
+  it('old block', async function () {
+    await mine();
+
+    const mostRecentBlock = await ethers.provider.getBlock('latest');
+
+    // Call the history address with the most recent block hash
+    await this.systemSigner.sendTransaction({
+      to: HISTORY_STORAGE_ADDRESS,
+      data: mostRecentBlock.hash,
+    });
+
+    await mineUpTo(mostRecentBlock.number + BLOCKHASH_SERVE_WINDOW + 10);
+
+    // Verify blockhash after setting history
+    await expect(this.mock.$blockHash(mostRecentBlock.number)).to.eventually.equal(mostRecentBlock.hash);
+  });
+
+  it('very old block', async function () {
+    await mine();
+
+    const mostRecentBlock = await ethers.provider.getBlock('latest');
+    await mineUpTo(mostRecentBlock.number + HISTORY_SERVE_WINDOW + 10);
+
+    await expect(this.mock.$blockHash(mostRecentBlock.number)).to.eventually.equal(ethers.ZeroHash);
+  });
+
+  it('future block', async function () {
+    await mine();
+
+    const mostRecentBlock = await ethers.provider.getBlock('latest');
+    const blockToCheck = mostRecentBlock.number + 10;
+    await expect(this.mock.$blockHash(blockToCheck)).to.eventually.equal(ethers.ZeroHash);
+  });
+
+  it('unsupported chain', async function () {
+    await setCode(HISTORY_STORAGE_ADDRESS, '0x00');
+
+    const mostRecentBlock = await ethers.provider.getBlock('latest');
+    await mineUpTo(mostRecentBlock.number + BLOCKHASH_SERVE_WINDOW + 10);
+
+    await expect(this.mock.$blockHash(mostRecentBlock.number)).to.eventually.equal(ethers.ZeroHash);
+    await expect(this.mock.$blockHash(mostRecentBlock.number + 20)).to.eventually.not.equal(ethers.ZeroHash);
+  });
+});