[HLE] Fix StoreData layout and implement IDatabaseService.Append (#43)

- Fixes `StoreData` layout/update handling so `UpdateLatest` returns the stored Mii data correctly.
- Implements `IDatabaseService.Append` (https://switchbrew.org/wiki/Shared_Database_services#IDatabaseService)

Also adds regression tests for `UpdateLatest` and `Append`.

(Might) fix Mario Kart 8 Deluxe crashing on first boot due to failed Mii verification check (due to custom Mii from emulator), and potentially Tomodachi Life: Living the Dream for the "Import Mii from system" option.

Co-authored-by: yell0wsuit <5692900+yell0wsuit@users.noreply.github.com>
Reviewed-on: https://git.ryujinx.app/projects/Ryubing/pulls/43

src/Ryujinx.HLE/HOS/Services/Mii/DatabaseImpl.cs

@@ -81,8 +81,10 @@ namespace Ryujinx.HLE.HOS.Services.Mii
             return ResultCode.Success;
         }
 
-        public ResultCode UpdateLatest<T>(DatabaseSessionMetadata metadata, IStoredData<T> oldMiiData, SourceFlag flag, IStoredData<T> newMiiData) where T : unmanaged
+        public ResultCode UpdateLatest<T>(DatabaseSessionMetadata metadata, T oldMiiData, SourceFlag flag, out T newMiiData) where T : unmanaged, IStoredData<T>
         {
+            newMiiData = default;
+
             if (!flag.HasFlag(SourceFlag.Database))
             {
                 return ResultCode.NotFound;
@@ -106,7 +108,7 @@ namespace Ryujinx.HLE.HOS.Services.Mii
 
                 newMiiData.SetFromStoreData(storeData);
 
-                if (oldMiiData == newMiiData)
+                if (oldMiiData.Equals(newMiiData))
                 {
                     return ResultCode.NotUpdated;
                 }
@@ -286,6 +288,18 @@ namespace Ryujinx.HLE.HOS.Services.Mii
             return result;
         }
 
+        public ResultCode Append(DatabaseSessionMetadata metadata, CharInfo charInfo)
+        {
+            ResultCode result = _miiDatabase.Append(metadata, _utilityImpl, charInfo);
+
+            if (result == ResultCode.Success)
+            {
+                result = _miiDatabase.SaveDatabase();
+            }
+
+            return result;
+        }
+
         public ResultCode ConvertCharInfoToCoreData(CharInfo charInfo, out CoreData coreData)
         {
             coreData = new CoreData();