dillon1000/react

Apply pending updates in order of priority

The queue maintains a pointer to the last progressed update in the list.
Updates that come after that pointer are pending. The pointer is set to
the end of the list during reconciliation.

Pending updates are sorted by priority then insertion. Progressed
updates are sorted by the order in which they were applied during
reconciliation, which may not be by priority: if a component bails out
before the updates are committed, in the next render, the progressed
updates are applied in the same order that they were previously, even if
a higher priority update comes in.

Once a progressed update is flushed/committed, it's removed from
the queue.