rust: prelude: re-export `core::mem::{align,size}_of{,_val}`

Rust 1.80.0 added:

    align_of
    align_of_val
    size_of
    size_of_val

from `core::mem` to the prelude [1].

For similar reasons, and to minimize potential confusion when code may
work in later versions but not in our current minimum, add it to our
prelude too.

Link: https://github.com/rust-lang/rust/pull/123168 [1]
Link: https://lore.kernel.org/rust-for-linux/CANiq72kOLYR2A95o0ji2mDmEqOKh9e9_60zZKmgF=vZmsW6DRg@mail.gmail.com/

 [2]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Andreas Hindborg <a.hindborg@kernel.org>
Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>