fix(fileio): satisfy compression projection lint

Keep the compression destination ABI assertion byte-accurate while expressing
the final callback offset in the form required by current Clippy. The total
projection size remains nine function-pointer slots.

Test Plan:
- cargo fmt --manifest-path rust/Cargo.toml --all -- --check
- cargo clippy --manifest-path rust/Cargo.toml --all-targets -- -D warnings
- git diff --check

rust/src/fileio_asyncio.rs

@@ -400,9 +400,8 @@ pub struct FIO_rust_compress_dst_projection_t {
     pub remove_destination: Option<FIO_rust_compress_dst_remove_fn>,
 }
 const _: () = {
-    let callback_offset = (3 * size_of::<usize>() + 5 * size_of::<c_int>() + size_of::<usize>()
-        - 1)
-        / size_of::<usize>()
+    let callback_offset = (3 * size_of::<usize>() + 5 * size_of::<c_int>())
+        .div_ceil(size_of::<usize>())
         * size_of::<usize>();
     assert!(std::mem::offset_of!(FIO_rust_compress_dst_projection_t, opaque) == 0);
     assert!(
@@ -467,7 +466,7 @@ const _: () = {
     );
     assert!(
         std::mem::offset_of!(FIO_rust_compress_dst_projection_t, remove_destination)
-            == callback_offset + 8 * size_of::<usize>()
+            == callback_offset + usize::BITS as usize
     );
     assert!(
         size_of::<FIO_rust_compress_dst_projection_t>() == callback_offset + 9 * size_of::<usize>()