Make ERC20Votes independent from ERC20Permit (#3816)

Co-authored-by: Francisco <frangio.1@gmail.com>

contracts/utils/Checkpoints.sol

@@ -68,6 +68,13 @@ library Checkpoints {
         return pos == 0 ? 0 : _unsafeAccess(self._checkpoints, pos - 1)._value;
     }
 
+    /**
+     * @dev Returns checkpoint at given position.
+     */
+    function getAtPosition(History storage self, uint32 pos) internal view returns (Checkpoint memory) {
+        return self._checkpoints[pos];
+    }
+
     /**
      * @dev Pushes a value onto a History so that it is stored as the checkpoint for the current block.
      *

contracts/utils/Nonces.sol

@@ -0,0 +1,31 @@
+// SPDX-License-Identifier: MIT
+pragma solidity ^0.8.0;
+
+import "./Counters.sol";
+
+/**
+ * @dev Provides tracking nonces for addresses. Nonces will only increment.
+ */
+abstract contract Nonces {
+    using Counters for Counters.Counter;
+
+    mapping(address => Counters.Counter) private _nonces;
+
+    /**
+     * @dev Returns an address nonce.
+     */
+    function nonces(address owner) public view virtual returns (uint256) {
+        return _nonces[owner].current();
+    }
+
+    /**
+     * @dev Consumes a nonce.
+     *
+     * Returns the current value and increments nonce.
+     */
+    function _useNonce(address owner) internal virtual returns (uint256 current) {
+        Counters.Counter storage nonce = _nonces[owner];
+        current = nonce.current();
+        nonce.increment();
+    }
+}