rust: Add vlcrs-core Crate and Abstractions for vlc_object_t

This Merge Request adds the vlcrs-core crate, which helps create safe ways to work with VLC's C functions and definitions. This crate makes it easier to use VLC features in Rust without directly dealing with unsafe C code.

It also includes Rust abstractions for vlc_object_t, making it simpler and safer to handle VLC objects in Rust.