dillon1000/react

[Flight] Include I/O not awaited in user space (#33715)

If I/O is not awaited in user space in a "previous" path we used to just
drop it on the floor. There's a few strategies we could apply here. My
first commit just emits it without an await but that would mean we don't
have an await stack when there's no I/O in a follow up.

I went with a strategy where the "previous" I/O is used only if the
"next" didn't have I/O. This may still drop I/O on the floor if there's
two back to back within internals for example. It would only log the
first one even though the outer await may have started earlier.

It may also log deeper in the "next" path if that had user space stacks
and then the outer await will appear as if it awaited after.

So it's not perfect.