dillon1000/react

[Fizz] Track abort state on Request (#36583)

Previously Fizz represented an active abort using the `ABORTING` request
status. This is ambiguous because aborting a task can synchronously
fatal the request, transitioning it to `CLOSING` or `CLOSED` while
another task is still unwinding from the same abort. Once that happened,
the in-flight task no longer observed that the request was aborted and
could fail to report its abort error.

This change removes the `ABORTING` status and instead tracks whether the
request was aborted independently on the Request. The existing
`fatalError` field continues to store the abort reason. As a result,
tasks that were rendering when an abort occurred continue to observe the
abort even if another aborted task has already fataled the request,
allowing all relevant unfinished task errors to be reported. DEV stalled
replays temporarily mask the aborted state so they can continue to
reconstruct suspended call sites as before.

This also establishes explicit abort state on the Request for follow-up
work that delays abort completion and allows rejected suspended work to
provide more specific abort errors.