Sends `SIGTERM` (graceful shutdown) instead of the existing `kill()`
which sends `SIGKILL`. Mirrors the `trio.Process.terminate()`
/ `multiprocessing.Process.terminate()` interface.
Used by `ActorNursery.cancel()`'s per-child escalation when
`Portal.cancel_actor()` raises `ActorTooSlowError`, and by the legacy
`hard_kill=True` branch. Swallows `ProcessLookupError` (child already
dead) same as `kill()`.
(this patch was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code
(cherry picked from commit 4c00913b3b)
Gud Boi
fcb0ff0dfd