[Base] Add user-literals for several memory sizes

Rather than using `n * 1024 * 1024`, this adds a convenient `_MiB`/`_KiB` user-literal to the new `literals.h` header to concisely describe units of memory in a much more readable way. Any other useful literals can be added to this header. These literals exist in the `xe::literals` namespace so they are opt-in, similar to `std::chrono` literals, and require a `using namespace xe::literals` statement to utilize it within the current scope.

I've done a pass through the codebase to replace trivial instances of `1024 * 1024 * ...` expressions being used but avoided anything that added additional casting complexity from `size_t` to `uint32_t` and such to keep this commit concise.

src/xenia/base/arena.h

@@ -14,11 +14,15 @@
 #include <cstdint>
 #include <vector>
 
+#include "xenia/base/literals.h"
+
 namespace xe {
 
+using namespace xe::literals;
+
 class Arena {
  public:
-  explicit Arena(size_t chunk_size = 4 * 1024 * 1024);
+  explicit Arena(size_t chunk_size = 4_MiB);
   ~Arena();
 
   void Reset();