misc: use prelude size_of

size_of is part of std::prelude as of Rust 1.80 (with size_of_val,
align_of, align_of_val), and the workspace MSRV is 1.89, so qualifying
it (mem::size_of, std::mem::size_of, core::mem::size_of) is unnecessary.

Convert every qualified size_of call-site to the bare prelude form and
drop the now-redundant `use std::mem::size_of;` imports, keeping
`use std::mem;` where it still serves non-prelude items (transmute,
swap, replace, take, zeroed, MaybeUninit, offset_of). size_of is the
only one of the four currently used in the tree.

Pure refactor, no behavioural change. Follow-up to the
clippy::absolute_paths cleanup (#7670), as discussed in #8444.

Signed-off-by: Henry Hrvoje Tonkovac <htonkovac@gmail.com>
Assisted-by: Claude:Opus-4.8

block/src/formats/qcow/internal/header.rs

@@ -10,7 +10,6 @@
 
 use std::fmt::{Display, Formatter, Result as FmtResult};
 use std::io::{Read, Seek, SeekFrom, Write};
-use std::mem::size_of;
 use std::str::FromStr;
 
 use bitflags::bitflags;

block/src/formats/qcow/internal/mod.rs

@@ -17,7 +17,6 @@ use std::cmp::{max, min};
 use std::fmt::{Debug, Formatter, Result as FmtResult};
 use std::fs::{OpenOptions, read_link};
 use std::io::{self, Seek, SeekFrom};
-use std::mem::size_of;
 use std::os::fd::AsRawFd;
 use std::path::Path;
 use std::{result, str};

block/src/formats/qcow/internal/qcow_raw_file.rs

@@ -6,7 +6,6 @@
 
 use std::fmt::Debug;
 use std::io::{self, BufWriter, Read, Seek, SeekFrom, Write};
-use std::mem::size_of;
 use std::os::fd::{AsFd, AsRawFd, BorrowedFd, RawFd};
 
 use byteorder::{BigEndian, ReadBytesExt, WriteBytesExt};
@@ -364,14 +363,13 @@ impl AsFd for QcowRawFile {
 #[cfg(test)]
 mod unit_tests {
     use std::io::{Read, Seek, SeekFrom};
-    use std::mem;
 
     use vmm_sys_util::tempfile::TempFile;
 
     use super::*;
 
     fn be_bytes(entries: &[u64]) -> Vec<u8> {
-        let mut v = Vec::with_capacity(mem::size_of_val(entries));
+        let mut v = Vec::with_capacity(size_of_val(entries));
         for e in entries {
             v.extend_from_slice(&e.to_be_bytes());
         }

block/src/formats/vhdx/internal/bat.rs

@@ -2,7 +2,6 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 
-use std::mem::size_of;
 use std::os::unix::fs::FileExt;
 use std::{io, result};
 

block/src/formats/vhdx/internal/header.rs

@@ -3,7 +3,6 @@
 // SPDX-License-Identifier: Apache-2.0
 
 use std::collections::btree_map::BTreeMap;
-use std::mem::size_of;
 use std::os::unix::fs::FileExt;
 use std::{io, result, slice};
 

block/src/formats/vhdx/internal/metadata.rs

@@ -2,7 +2,6 @@
 //
 // SPDX-License-Identifier: Apache-2.0
 
-use std::mem::size_of;
 use std::os::unix::fs::FileExt;
 use std::{io, result};