Call fdnotifier.UpdateFD() from fsimpl/gofer.specialFileFD.
Call fdnotifier.UpdateFD() from fsimpl/gofer.specialFileFD.

The fdnotifier package provides an API to a thread that continually epolls
arbitrary host FDs. The set of events polled for each host FD is (intended to
be) all events for which a waiter.Entry has expressed interest, as returned by
waiter.Queue.Events() for the waiter.Queue registered to the given host FD.
When the set of events changes (due to a change in the set of registered
waiter.Entries), the mutator must call fdnotifier.UpdateFD() to recalculate the
new event set and propagate it to the epoll FD.

PiperOrigin-RevId: 319924719

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