[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/threading.h

@@ -25,11 +25,14 @@
 #include <vector>
 
 #include "xenia/base/assert.h"
+#include "xenia/base/literals.h"
 #include "xenia/base/platform.h"
 
 namespace xe {
 namespace threading {
 
+using namespace xe::literals;
+
 #if XE_PLATFORM_ANDROID
 void AndroidInitialize();
 void AndroidShutdown();
@@ -368,7 +371,7 @@ struct ThreadPriority {
 class Thread : public WaitHandle {
  public:
   struct CreationParameters {
-    size_t stack_size = 4 * 1024 * 1024;
+    size_t stack_size = 4_MiB;
     bool create_suspended = false;
     int32_t initial_priority = 0;
   };