msg.sender breaks meta transactions in operator-filter registry

[zcstarr]

Summary:
The use of msg.sender in the operator-filter registry makes it impossible to inherit from these classes and override msg.sender. This can be a problem in contexts where the sender may be different than anticipated, such as with EIP-725X.

As a solution, it is recommended to follow the example of OpenZeppelin's contracts and use _msgSender() instead. This will make it easier to consume the operator-filter registry without having to fork the code.

Reference: https://forum.openzeppelin.com/t/why-use-msgsender-rather-than-msg-sender/4370