Work around unused_qualifications lint for Rust 1.80 prelude extension

`size_of(_val)()` was added to the prelude in Rust 1.80, causing
`unused_qualifications` warnings whenever we qualify a call to it with
via `std::mem::size_of_val()`.

The easiest workaround is to remove the prefix and explicitly import the
function in scope.  We annotate the import with a `TODO` to remove it
once bumping our MSRV on or past 1.80.

src/d3d12/mod.rs

@@ -1,4 +1,10 @@
-use std::{backtrace::Backtrace, fmt, sync::Arc};
+use std::{
+    backtrace::Backtrace,
+    fmt,
+    // TODO: Remove when bumping MSRV to 1.80
+    mem::size_of_val,
+    sync::Arc,
+};
 
 use log::{debug, warn, Level};
 use windows::Win32::{
@@ -628,7 +634,7 @@ impl Allocator {
             device.CheckFeatureSupport(
                 D3D12_FEATURE_D3D12_OPTIONS,
                 <*mut D3D12_FEATURE_DATA_D3D12_OPTIONS>::cast(&mut options),
-                std::mem::size_of_val(&options) as u32,
+                size_of_val(&options) as u32,
             )
         }
         .map_err(|e| {