Add security_attributes() to windows::OpenOptionsExt

Proposal

Problem statement

There is currently no means, using std::fs, to provide SECURITY_ATTRIBUTES when opening a file. A private implementation of OpenOptions do have a security_attributes function but it is not expose through the OpenOptionExt trait. In order to provide a SECURITY_ATTRIBUTES, one must use the windows crate directly calling C ffi bindings.

Motivating examples or use cases

let file = std::fs::File::options()
    .access_mode(1179785u32) // FILE_GENERIC_READ
    .share_mode(0) // FILE_SHARE_NONE
    // no means to pass security attributes to add more security.
    .open("foo.txt").unwrap();

Solution sketch

Extends OpenOptionsExt for windows

pub trait OpenOptionsExt {
    // Required methods
    fn [access_mode](https://doc.rust-lang.org/std/os/windows/fs/trait.OpenOptionsExt.html#tymethod.access_mode)(&mut self, access: [u32](https://doc.rust-lang.org/std/primitive.u32.html)) -> [&mut Self](https://doc.rust-lang.org/std/primitive.reference.html);
    // ...

   fn security_attributes(&mut self, attributes: SECURITY_ATTRIBUTES) -> &mut Self;
}

let attributes = // ...;

let file = std::fs::File::options()
    .access_mode(1179785u32) // FILE_GENERIC_READ
    .share_mode(0) // FILE_SHARE_NONE
    .security_attributes(attributes)
    .open("foo.txt").unwrap();

Links and related work

windows_security.go

Design issue

The main design issue I see is how to provide a safe way to create security attributes.

Start with the Windows OpenOptionsExt trait and the existing private OpenOptions security_attributes implementation described in the issue. Determine a safe public representation for SECURITY_ATTRIBUTES and its ownership requirements; done means the trait exposes the capability without requiring direct windows-crate FFI, with appropriate coverage for the proposed usage.