Add Blockhash library following EIP-2935 (#5642)

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

contracts/mocks/BlockhashMock.sol

@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.20;
+
+import {Blockhash} from "../utils/Blockhash.sol";
+
+/// @dev This mock is required for upgradeable tests to pass
+contract BlockhashMock {
+
+}