test: test files with Zama gateway/fhevm config

contracts/test/token/ERC20/TestERC20Mintable.sol

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+// SPDX-License-Identifier: BSD-3-Clause-Clear
+pragma solidity ^0.8.24;
+
+import { ERC20 } from "@openzeppelin/contracts/token/ERC20/ERC20.sol";
+import { Ownable2Step, Ownable } from "@openzeppelin/contracts/access/Ownable2Step.sol";
+
+/**
+ * @title     ERC20Mintable
+ * @notice    This contract is an ERC20 token that is mintable by the owner.
+ */
+contract ERC20Mintable is ERC20, Ownable2Step {
+    /// @dev override number of decimals
+    uint8 private immutable _DECIMALS;
+
+    constructor(
+        string memory name_,
+        string memory symbol_,
+        uint8 decimals_,
+        address owner_
+    ) ERC20(name_, symbol_) Ownable(owner_) {
+        _DECIMALS = decimals_;
+    }
+
+    /**
+     * @notice Returns the number of decimals.
+     */
+    function decimals() public view override returns (uint8) {
+        return _DECIMALS;
+    }
+
+    /**
+     * @notice              Mint tokens.
+     * @param amount        Amount of tokens to mint.
+     */
+    function mint(uint256 amount) public onlyOwner {
+        _mint(msg.sender, amount);
+    }
+}

contracts/test/token/ERC20/TestEncryptedERC20Wrapped.sol

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+// SPDX-License-Identifier: BSD-3-Clause-Clear
+pragma solidity ^0.8.24;
+
+import { EncryptedERC20Wrapped } from "../../../token/ERC20/EncryptedERC20Wrapped.sol";
+import { DefaultFHEVMConfig } from "../../DefaultFHEVMConfig.sol";
+import { DefaultGatewayConfig } from "../../DefaultGatewayConfig.sol";
+
+contract TestEncryptedERC20Wrapped is DefaultFHEVMConfig, DefaultGatewayConfig, EncryptedERC20Wrapped {
+    constructor(address erc20_) EncryptedERC20Wrapped(erc20_) {
+        //
+    }
+}

contracts/test/token/ERC20/TestEncryptedWETH.sol

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+// SPDX-License-Identifier: BSD-3-Clause-Clear
+pragma solidity ^0.8.24;
+
+import { EncryptedWETH } from "../../../token/ERC20/EncryptedWETH.sol";
+import { DefaultFHEVMConfig } from "../../DefaultFHEVMConfig.sol";
+import { DefaultGatewayConfig } from "../../DefaultGatewayConfig.sol";
+
+/* solhint-disable no-empty-blocks*/
+contract TestEncryptedWETH is DefaultFHEVMConfig, DefaultGatewayConfig, EncryptedWETH {}