Kernel: Declare type aliases with "using" instead of "typedef"

This is the idiomatic way to declare type aliases in modern C++.
Flagged by Sonar Cloud as a "Code Smell", but I happen to agree
with this particular one. :^)

Kernel/Process.h

@@ -80,7 +80,7 @@ enum class VeilState {
     Locked,
 };
 
-typedef HashMap<FlatPtr, RefPtr<FutexQueue>> FutexQueues;
+using FutexQueues = HashMap<FlatPtr, RefPtr<FutexQueue>>;
 
 struct LoadResult;