Googletest export

[fdio] Improve fdio_pipe_half signature, step 3.

The return value on fdio_pipe_half conflated two things: the error code
on failure (as a zx_status_t) or a file descriptor on success. This
technically worked, because they're both ints, the error code was always
negative, and the file descriptor always positive. However, the stated
return type of zx_status_t was misleading. This changes the signature
such that it always returns an actual zx_status_t, and the file
descriptor is returned through a pointer argument.

Also remove the last argument, since it was always given the same value.

This needs to be done as a soft transition because it's called from the
Dart runtime, from googletest, and from Crashpad, and Crashpad and
Chromium both depend on googletest on Fuchsia. The steps are as follows:

1. Add fdio_pipe_half2.
2. Update Dart to use fdio_pipe_half2.
3. Update googletest to use fdio_pipe_half2.
4. Roll updated googletest into Chronium.
5. Update Crashpad to use fdio_pipe_half2 and roll updated googletest into it.
6. Update fdio_pipe_half to match fdio_pipe_half2.
7. Update Dart to use fdio_pipe_half again.
8. Update googletest to use fdio_pipe_half again.
9. Roll updated googletest into Chronium.
10. Update Crashpad to use fdio_pipe_half again and roll updated googletest into it.
11. Remove fdio_pipe_half2.

This is step 3.

PiperOrigin-RevId: 241957137