dillon1000/react

Prefer reporting conditional hook violations over "hook as value" violations

After running the latest hook validation internally, I found some cases where 
there was a violation but the error message was not ideal. For example on this 
code: 

```javascript 

usePossiblyNullHook?.(); 

``` 

We reported a "hooks can't be used as normal values" violation, when we'd 
ideally report a "hooks can't be called conditionally" violation. The solution 
in this PR is to track errors by source location, and upgrade the former 
violation to the latter, more serious violation. See fixtures for examples.