dillon1000/react

Optimization for scope merging when no deps

Addresses T168684688 (#2242). MergeReactiveScopesThatInvalidateTogether does not 
merge scopes if their output is not guaranteed to change when their inputs do. 
So for example a case such as `{session_id: bar(props.bar)}` will not merge the 
scopes for `t0 = bar(props.bar)` and `t1 = {session_id: t0}`, because t0 isn't 
guaranteed to change when `props.bar` does, and we want to avoid recreating the 
t1 object unless it semantically changes. 

But there's a special case: if a scope has no dependencies, then we'll never 
execute it again anyway. So it doesn't matter what kind of value it produces and 
it's safe to merge with subsequent scopes: 

```javascript 

return {session_id: bar()} 

``` 

Without the reactive input, `bar()` will always return the same value since 
we'll only ever call it once anyway. So it's safe to then merge with the scope 
for the outer object literal.