Closes #38168
Closes #42414

We were already using `ExitStatusExt::from_raw()` to construct an
`ExitStatus`, but we were passing in the exit code from
alacritty_terminal's `ChildExit` event. This worked fine on Windows
where `from_raw()` expects an exit code, but on Unix, `from_raw()`
([read
more](https://doc.rust-lang.org/std/os/unix/process/trait.ExitStatusExt.html#tymethod.from_raw))
expects a raw wait status from `waitpid()` and not an exit code.

When a child process was killed by a signal (e.g., SIGSEGV),
`ExitStatus::code()` returns `None` since only normal exits have an exit
code. This caused the terminal to hang because we weren't properly
detecting the exit.

One fix would have been to remove the dependency on `ExitStatus`
entirely, but using the raw wait status gives us more information, we
can now detect exit codes, signal terminations, and more.

The actual fix was upstream in `alacritty_terminal` to send the raw wait
status instead of just the exit code.

Currently using forked patch
https://github.com/zed-industries/alacritty/tree/v0.16-child-exit-patch
which is based on v0.25.1.

Upstream PR: https://github.com/alacritty/alacritty/pull/8825

Release Notes:

- Fixed terminal hanging when a child process is killed by a signal
(e.g., SIGSEGV from null pointer dereference).