[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/gpu/vulkan/texture_cache.cc

@@ -12,6 +12,7 @@
 #include <algorithm>
 
 #include "third_party/fmt/include/fmt/format.h"
+#include "xenia/base/literals.h"
 #include "xenia/base/logging.h"
 #include "xenia/base/math.h"
 #include "xenia/base/memory.h"
@@ -36,8 +37,10 @@ namespace vulkan {
 
 using xe::ui::vulkan::CheckResult;
 
+using namespace xe::literals;
+
 constexpr uint32_t kMaxTextureSamplers = 32;
-constexpr VkDeviceSize kStagingBufferSize = 64 * 1024 * 1024;
+constexpr VkDeviceSize kStagingBufferSize = 64_MiB;
 
 const char* get_dimension_name(xenos::DataDimension dimension) {
   static const char* names[] = {