Make TransparentUpgradeableProxy work with existing ProxyAdmins

[Arvolear]

🧐 Motivation

Currently, the TransparentUpgradeableProxy deploys the ProxyAdmin every time in the constructor. It would be great if it were possible to pass the existing ProxyAdmin address for reuse.

📝 Details

The current constructor logic is the following:

contract TransparentUpgradeableProxy is ERC1967Proxy {
    ...

    constructor(address _logic, address initialOwner, bytes memory _data) payable ERC1967Proxy(_logic, _data) {
        _admin = address(new ProxyAdmin(initialOwner));

        ERC1967Utils.changeAdmin(_proxyAdmin());
    }

    ...
}

Propose a slight modification:

contract TransparentUpgradeableProxy is ERC1967Proxy {
    ...

    constructor(
        address _logic,
        address initialOwnerOrAdmin,
        bool isOwner,
        bytes memory _data
    ) payable ERC1967Proxy(_logic, _data) {
        if (isOwner) {
            _admin = address(new ProxyAdmin(initialOwnerOrAdmin));
        } else {
            _admin = initialOwnerOrAdmin;
        }

        ERC1967Utils.changeAdmin(_proxyAdmin());
    }

    ...
}

This would allow various transparent proxies to be used in factories when a single contract is responsible for their management.