[DevTools] Track Server Environment Names of Each SuspenseNode (#34605)

Tracks the environment names of the I/O in each SuspenseNode and sent it
to the front end when the suspenders change.

In the front end, every child boundary should really be treated as it
has all environment names of the parents too since they're blocked by
the parent too. We could do this tracking on backend but if there's ever
one added on the root would need to be send for every child.

This lets us highlight which subtrees are blocked by content on the
server.

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Co-authored-by: Sebastian "Sebbie" Silbermann <silbermann.sebastian@gmail.com>