block: Rename AsyncDiskFile::new_async_io to create_async_io

The new_ prefix in Rust conventionally denotes constructors that return
Self (e.g. Vec::new(), File::new()). AsyncDiskFile::new_async_io does
not return Self. It is a factory method that constructs and returns a
Box<dyn AsyncIo> worker bound to the disk file descriptor and
metadata. The create_ prefix communicates this: the caller receives
a freshly constructed object of a different type.

This rename touches every format backend in block plus two external
callers in virtio-devices and performance-metrics. Every change is a
mechanical s/new_async_io/create_async_io/ substitution. No functional
change.

Ref: #7877 (task 3.2.8)
Signed-off-by: Anatol Belski <anbelski@linux.microsoft.com>

virtio-devices/src/block.rs

@@ -1129,7 +1129,7 @@ impl VirtioDevice for Block {
                 mem: mem.clone(),
                 disk_image: self
                     .disk_image
-                    .new_async_io(queue_size as u32)
+                    .create_async_io(queue_size as u32)
                     .map_err(|e| {
                         error!("failed to create new AsyncIo: {e}");
                         ActivateError::BadActivate