What to do about trio.Process.aclose()?

[goodboy]

It's been deprecated since 0.20.0 and we need to implement hard kill
semantics ourselves now instead of relying on the prior
trio.Process.aclose() wrapping; see #330!

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Progress

• we need to sync with trio upstream to figure out what the plan is
  for getting the functionality out of the old Process.aclose() if we
  still need it in our spawning layer.
  • see trio.Process deprecations #330 for the details on all that and history behind the api
    changes in trio.
• First commit is just directly calling trio.Process.aclose() directly
  for now what was an attempt to fix the mypy run..
• copy out the old .aclose() implementation into our
  do_hard_kill() with comments on the original source.
• get mypy run clean!
• nooz file 😎