dillon1000/react

SuspenseList Optimizations (#16005)

* Add a bunch of optimizations to SuspenseList

We now are able to bail out of reconciliation and splitting out the tail
during deep updates that hasn't changed the child props. This only
works while the list wasn't suspended before.

I also moved the second render of the "head" to the complete phase. This
cleans it up a bit for the tail collapsing PR.

For this second pass I also use a new technique of resetting the child
Fibers for the second pass. This is effectively a fast path to avoid
reconciling the children against props again.

* Move to didSuspend from SuspenseListState to the effectTag

The effectTag now tracks whether the previous commit was suspended.

This frees up SuspenseListState to be render-phase only state.

We use null to mean the default "independent" mode.

* Rename to SuspenseListState to SuspenseListRenderState

* Reuse SuspenseListRenderState across render passes

* Add optimization to bail out of scanning children if they can't be suspended

This optimized the deep update case or initial render without anything
suspending.

We have some information available to us that tell us if nothing has
suspended in the past and nothing has suspended this render pass.

This also fixes a bug where we didn't tag the previous render as having
suspended boundaries if we didn't need to force a rerender.

* rm printChildren

oops