Miri: Add CreateWaitableTimerEx stub

This function will always fail, allowing std's `Sleep` fallback path to be taken instead.

src/tools/miri/src/shims/windows/foreign_items.rs

@@ -267,6 +267,12 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriInterpCxExt<'mir, 'tcx> {
 
                 this.Sleep(timeout)?;
             }
+            "CreateWaitableTimerExW" => {
+                let [_attributes, _name, _flags, _access] =
+                    this.check_shim(abi, Abi::System { unwind: false }, link_name, args)?;
+                // Unimplemented. Always return failure.
+                this.write_null(dest)?;
+            }
 
             // Synchronization primitives
             "AcquireSRWLockExclusive" => {