We previously introduced new infrastructure for sharing code in
`aes_common.rs` among AES algorithms.
This patch makes AES-KW algorithm adapt the new infrastructure, by
moving the relevant code away from `aes_operation.rs` to its own
`aes_kw_operation.rs`, and calling AES common steps in the new
`aes_common.rs`.
Since all AES algorithms have been moved away from `aes_operation.rs`,
the file `aes_operation.rs` is also removed. The key handle variants
`Handle::Aes128`, `Handle::Aes192` and `Handle::Aes256` used by the old
AES infrastructure is also removed.
Testing: Refactoring. Existing tests suffice.
Fixes: Part of #41763
Signed-off-by: Kingsley Yung <kingsley@kkoyung.dev>