dillon1000/react

[be] Hook type inference should only happen at LoadGlobal

--- 

#1254 added inference for hooks loaded from globals. This is the only time we 
need to generate a type equation assigning `lval` to a resolved`Hook` type. 

@gsathya Would love to get your feedback here on the change. From my 
understanding, this change is technically incorrect, since the type equation we 
generate should be dependent on the `callee` type (i.e. `Hook` if callee is a 
hook, `Function` if callee is a function). 

Would the next step be to consolidate `Hook` and `Function` types? 

```js 

type Function { 

... 

isHook: boolean, // set by inference 

} 

type FunctionSignature { 

isHook: boolean, // set when adding to ShapeRegistry 

} 

```