Add support for EIP-7201 namespaces

contracts/namespaces.sol

@@ -0,0 +1,62 @@
+// SPDX-License-Identifier: UNLICENSED
+pragma solidity ^0.8.20;
+
+contract C1 {
+}
+
+contract C2 {
+    event B();
+
+    struct A { uint z; }
+
+    uint constant C = 3;
+    // a
+    uint x;
+    // b
+    /// @custom:oz-upgrades-unsafe-allow state-variable-immutable
+    uint immutable y = 2;
+    uint private z;
+
+    string private s1 = "";
+
+    function f() public {
+        z = 3;
+    }
+
+    function g() public {
+    }
+}
+
+contract C3 {
+    address private x;
+}
+
+contract C4 {
+    address private x;
+    constructor() {
+        x = msg.sender;
+    }
+}
+
+contract C5 {
+    address private x = msg.sender;
+}
+
+contract C6 {
+}
+
+contract C7 {
+    uint x; // a comment
+
+    uint y;
+    // a separate comment
+}
+
+contract C8 {
+    address private x;
+    address private y = address(this);
+
+    constructor() {
+        x = msg.sender;
+    }
+}

hardhat.config.js

@@ -9,6 +9,6 @@ internalTask(TASK_COMPILE_SOLIDITY_GET_COMPILER_INPUT, async (args, hre, runSupe
 
 module.exports = {
   solidity: {
-    compilers: [{ version: '0.6.7' }, { version: '0.8.8' }],
+    compilers: [{ version: '0.6.7' }, { version: '0.8.8' }, { version: '0.8.20' }],
   },
 };