rust: alloc: implement kernel Vec type

`Vec` provides a contiguous growable array type (such as `Vec`) with
contents allocated with the kernel's allocators (e.g. `Kmalloc`,
`Vmalloc` or `KVmalloc`).

In contrast to Rust's `Vec` type, the kernel `Vec` type considers the
kernel's GFP flags for all appropriate functions, always reports
allocation failures through `Result<_, AllocError>` and remains
independent from unstable features.

Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20240816001216.26575-14-dakr@kernel.org

Author: Danilo Krummrich

rust/kernel/alloc.rs

@@ -5,6 +5,7 @@
 #[cfg(not(any(test, testlib)))]
 pub mod allocator;
 pub mod kbox;
+pub mod kvec;
 pub mod vec_ext;
 
 #[cfg(any(test, testlib))]
@@ -18,6 +19,11 @@ pub use self::kbox::KBox;
 pub use self::kbox::KVBox;
 pub use self::kbox::VBox;
 
+pub use self::kvec::KVVec;
+pub use self::kvec::KVec;
+pub use self::kvec::VVec;
+pub use self::kvec::Vec;
+
 /// Indicates an allocation error.
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
 pub struct AllocError;