dillon1000/react

[Fizz] Reset the segent id assignment when postponing the root (#33755)

When postponing the root we encode the segment Id into the postponed
state but we should really be reseting it to zero so we can restart the
counter from the beginning when the resume is actually just a re-render.

This also no longer assigns the root segment id based on the postponed
state when resuming the root for the same reason. In the future we may
use the embedded replay segment id if we implement resuming the root
without re-rendering everything but that is not yet implemented or
planned.