rust: list: Add an example for `ListLinksSelfPtr` usage

It appears that the support for `ListLinksSelfPtr` is dead code at the
moment [1]. Hence add an example similar to `ListLinks` usage to help
catching bugs and demonstrating the usage.

The example is mostly based on Alice's usage in binder driver [2].

Link: https://lore.kernel.org/rust-for-linux/20250719183649.596051-1-ojeda@kernel.org/ [1]
Link: https://lore.kernel.org/rust-for-linux/20231101-rust-binder-v1-4-08ba9197f637@google.com/ [2]
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
1 file changed