windows: use syscall.SyscallN in Proc.Call

All the SyscallX functions are deprecated in favor of SyscallN. The
latter is easier to use, supports more arguments, and uses less stack.

Autogenerated wrappers already switch to SyscallN in https://go-review.googlesource.com/c/sys/+/691715.

Fixes golang/go#78317

Change-Id: I7e56e713d1c20558e9932d757299796836c9c04f
Reviewed-on: https://go-review.googlesource.com/c/sys/+/758700
Reviewed-by: Damien Neil <dneil@google.com>
Auto-Submit: Quim Muntal <quimmuntal@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>