dillon1000/react

Partially enable validateNoSetStateInRender

The approach i initially took to validating function expressions was to try to 
extend the mutable range if they are called during render, and then use the 
mutable range of a function to determine if it's called during render later. 
However there are cases where the range can be extended for other reasons, as 
@poteto discovered, so we can't rely on the range extension. We've had several 
of our validations completely off as a result of this. 

In this PR i'm re-enabling @poteto's ValidateNoSetStateInRender pass by default, 
but making the function expression checking use a separate compiler flag. This 
means we'll have some false negatives, but should guarantee that we avoid false 
positives. This means we can definitely catch things like: 

``` 

const [state, setState] = useState(false); 

setState(true); 

``` 

Which we would have allowed by default before.