[service, ns, acc] Stub IsQualificationTransitionSupportedByProcessId and SaveDataThumbnail commands

- ns: Stubbed IsQualificationTransitionSupportedByProcessId (2520) to always return true.
- acc: added the missing SaveDataThumbnail commands:
  * ClearSaveDataThumbnail (111) → stubbed, returns success.
  * LoadSaveDataThumbnail (112) → stubbed, returns success with size=0.
  * GetSaveDataThumbnailExistence (113) → stubbed, returns false.

This allows titles like Borderlands GOTY to progress past save-related errors.

src/core/hle/service/acc/acc.cpp

@@ -1116,25 +1116,26 @@ void Module::Interface::ClearSaveDataThumbnail(HLERequestContext& ctx) {
 }
 
 void Module::Interface::LoadSaveDataThumbnail(HLERequestContext& ctx) {
-    // TODO: Grab thumbnail from Nand so this can be unstubbed
-    // For now, pretend a thumbnail exists and return dummy data
-    std::vector<u8> dummy_thumbnail(THUMBNAIL_SIZE, 0);
-    ctx.WriteBuffer(dummy_thumbnail);
+    const auto out_size = ctx.GetWriteBufferSize();
 
-    LOG_WARNING(Service_ACC, "(STUBBED) called. returning dummy thumbnail");
+    LOG_WARNING(Service_ACC, "(STUBBED) called. out_size={}", out_size);
+
+    if (out_size > 0) {
+        std::vector<u8> dummy(out_size, 0);
+        ctx.WriteBuffer(dummy.data(), dummy.size());
+    }
 
     IPC::ResponseBuilder rb{ctx, 3};
     rb.Push(ResultSuccess);
-    rb.Push<u64>(THUMBNAIL_SIZE);
+    rb.Push<u64>(0);
 }
 
 void Module::Interface::GetSaveDataThumbnailExistence(HLERequestContext& ctx) {
-    // TODO: Get actual thumbnail image
-    LOG_WARNING(Service_ACC, "(STUBBED) called. Returning true (dummy thumbnail)");
+    LOG_WARNING(Service_ACC, "(STUBBED) called. Returning false.");
 
     IPC::ResponseBuilder rb{ctx, 3};
     rb.Push(ResultSuccess);
-    rb.Push<bool>(true);
+    rb.Push<bool>(false);
 }
 
 void Module::Interface::TrySelectUserWithoutInteractionDeprecated(HLERequestContext& ctx) {