Pull Rust updates from Miguel Ojeda:
 "More core additions, getting closer to a point where the first Rust
  modules can be upstreamed. The major ones being:

   - Sync: new types 'Arc', 'ArcBorrow' and 'UniqueArc'.

   - Types: new trait 'ForeignOwnable' and new type 'ScopeGuard'.

  There is also a substantial removal in terms of lines:

   - 'alloc' crate: remove the 'borrow' module (type 'Cow' and trait
     'ToOwned')"

* tag 'rust-6.3' of https://github.com/Rust-for-Linux/linux:
  rust: delete rust-project.json when running make clean
  rust: MAINTAINERS: Add the zulip link
  rust: types: implement `ForeignOwnable` for `Arc<T>`
  rust: types: implement `ForeignOwnable` for the unit type
  rust: types: implement `ForeignOwnable` for `Box<T>`
  rust: types: introduce `ForeignOwnable`
  rust: types: introduce `ScopeGuard`
  rust: prelude: prevent doc inline of external imports
  rust: sync: add support for dispatching on Arc and ArcBorrow.
  rust: sync: introduce `UniqueArc`
  rust: sync: allow type of `self` to be `ArcBorrow<T>`
  rust: sync: introduce `ArcBorrow`
  rust: sync: allow coercion from `Arc<T>` to `Arc<U>`
  rust: sync: allow type of `self` to be `Arc<T>` or variants
  rust: sync: add `Arc` for ref-counted allocations
  rust: compiler_builtins: make stubs non-global
  rust: alloc: remove the `borrow` module (`ToOwned`, `Cow`)