* `Initializable`: refactored implementation of modifiers for easier understanding. ([#3450](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3450))
* `Proxies`: remove runtime check of ERC1967 storage slots. ([#3455](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3455))
* `ERC165Checker`: add `supportsERC165InterfaceUnchecked` for consulting individual interfaces without the full ERC165 protocol. ([#3339](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3339))
* `Address`: optimize `functionCall` functions by checking contract size only if there is no returned data. ([#3469](https://github.com/OpenZeppelin/openzeppelin-contracts/pull/3469))