stdlib::child::Windows::ChildImp::try_wait shouldn't fail on timeout of GetQueuedCompletionStatus

[bmc-msft]

Per the documentation on GetQueuedCompletionStatus:

The number of milliseconds that the caller is willing to wait for a completion packet to appear at the completion port. If a completion packet does not appear within the specified time, the function times out, returns FALSE, and sets *lpOverlapped to NULL.

As such, calling wait_imp(0) as shown here:

command-group/src/stdlib/child/windows.rs

Line 91 in b704729

self.wait_imp(0)?;

Which calls GetQueuedCompletionStatus here:

command-group/src/stdlib/child/windows.rs

Lines 72 to 80 in b704729

	res_bool(unsafe {
	GetQueuedCompletionStatus(
	self.handles.completion_port,
	&mut code,
	&mut key,
	overlapped.as_mut_ptr(),
	timeout,
	)
	})?;

A timeout will result in FALSE, which results in an Err.

This is contrary to normal behavior for try_wait. I would expect the try_wait to not fail on GetQueuedCompletionStatus timeout, but instead act like underlying impl of try_wait and return an Ok(None), or handle non-timeout errors specifically.