Rewrite ggml in Rust

[thewh1teagle]

I think it could be a great time to consider rewriting ggml in Rust.

With coding agents becoming much stronger, the effort is more realistic now, and Rust could make the project safer in terms of memory safety while still keeping performance and low-level control.

It should also still be possible to expose a C API, so existing projects could keep using it without major changes.