Improve gas efficiency of SafeERC20.forceApprove when the token returns a bool on approve

[fedgiac]

🧐 Motivation

More gas-efficient implementation of SafeERC20.forceApprove in the case where the token returns a bool on approve.
Expected savings are a little more than a call to EXTCODESIZE, that is 2600 gas in the worst case of no access lists or 100 gas otherwise.
The required code changes are very small.

📝 Details

forceApprove is the only function calling _callOptionalReturnBool (code).
This function is supposed to behave like _callOptionalReturn except that if the inner call reverts then it returns false instead of reverting.
The output is currently computed as:

success && (returnsEmptyOutput || returnsBoolTrue) && targetHasCode

My proposal it to change this expression to:

success && ((returnsEmptyOutput && targetHasCode) || returnsBoolTrue)

With the proposed change, if returnsEmptyOutput is false then the evalutation of the second && short-circuits and the code is assumed to have code.
This is the same assumption made in _callOptionalReturn through functionCall.