Support solc v0.8.35 (#512)

- Support solc v0.8.35
- The new `erc7201` is comptime (already translated to a constant in
Yul)

Didn't spot any relevant breakage or addition in the release notes so
should be no-brainer.

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/integration/contracts/ERC7201.sol

@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.35;
+
+/* runner.json
+{
+    "differential": true,
+    "actions": [
+        {
+            "Instantiate": {
+                "code": {
+                    "Solidity": {
+                        "contract": "ERC7201"
+                    }
+                }
+            }
+        }
+    ]
+}
+*/
+
+/// Tests the `erc7201` builtin introduced in solc 0.8.35.
+/// Reference: https://eips.ethereum.org/EIPS/eip-7201
+contract ERC7201 {
+    /// Reference implementation of the ERC-7201 base slot formula in pure
+    /// Solidity. Used to cross-check the builtin output.
+    function referenceSlot(string memory id) internal pure returns (uint256) {
+        return uint256(
+            keccak256(bytes.concat(bytes32(uint256(keccak256(bytes(id))) - 1)))
+                & ~bytes32(uint256(0xff))
+        );
+    }
+
+    constructor() payable {
+        // Compile-time path: literal argument, solc folds the result into a
+        // numeric constant in the emitted Yul.
+        assert(erc7201("example.main") == referenceSlot("example.main"));
+        assert(
+            erc7201("erc7201:openzeppelin.storage.Initializable")
+                == referenceSlot("erc7201:openzeppelin.storage.Initializable")
+        );
+        assert(erc7201("") == referenceSlot(""));
+
+        // Runtime path: non-literal argument, solc emits a Yul utility
+        // function that performs the keccak256 hashes at runtime.
+        string memory id = "example.main";
+        assert(erc7201(id) == referenceSlot(id));
+
+        string memory empty = "";
+        assert(erc7201(empty) == referenceSlot(empty));
+
+        // The two paths must agree.
+        assert(erc7201("example.main") == erc7201(id));
+    }
+}