refactor: rewrite the whole rustc_smir::context

This commit removes the `Tables` field from `SmirCtxt`, since borrows of `tables` should only be managed by `SmirInterface`.

This change prevents `SmirCtxt` from holding separate borrows and requires passing `tables` explicitly when needed.

We use the `traits.rs` file to define traits that are used for encapsulating the associated functions in the rustc's internals. This is much easier to use and maintain than directly cramming everything into `SmirCtxt`.

Author: makai410