block_util: Port synchronous RAW file to AsyncIo trait

Based on the synchronous RAW file implementation present in the qcow
crate, we created a new raw_sync module in block_util that ports this
synchronous implementation to the AsyncIo trait.

The point is to reuse virtio-blk asynchronous implementation for both
synchronous and asynchronous backends.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

virtio-devices/src/seccomp_filters.rs

@@ -130,6 +130,7 @@ fn virtio_blk_io_uring_thread_rules() -> Result<Vec<SyscallRuleSet>, Error> {
         allow_syscall(libc::SYS_fsync),
         allow_syscall(libc::SYS_futex),
         allow_syscall(SYS_IO_URING_ENTER),
+        allow_syscall(libc::SYS_lseek),
         allow_syscall(libc::SYS_madvise),
         allow_syscall(libc::SYS_munmap),
         allow_syscall(libc::SYS_read),