std: Add IntoRaw{Fd,Handle,Socket} traits

std: Add IntoRaw{Fd,Handle,Socket} traits

This commit is an implementation of [RFC 1174][rfc] which adds three new traits
to the standard library:

* `IntoRawFd` - implemented on Unix for all I/O types (files, sockets, etc)
* `IntoRawHandle` - implemented on Windows for files, processes, etc
* `IntoRawSocket` - implemented on Windows for networking types

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/1174-into-raw-fd-socket-handle-traits.md

Closes #27062