dillon1000/react

[DevTools] Remove use of .alternate in root and recordProfilingDurations (#30895)

Ideally we shouldn't use the `.alternate` to access previous state
because ideally Fibers shouldn't have alternates.

The only case it's ok to use it is when it is used to identity the
stateful part of a component's identity. In a non-alternate Fiber model
there would instead be another object that represents instance but in
the current model it's modeled by the pair.

It's not ok is to get the previous state of the tree since that would
not live on the stateful part.

We don't generally need this though because we have the previous state
on instance.data before updating it, or passed from above.