Cleanup: Pass asset handle to asset iterator, rather than wrapped file

This iterator was introduced before `AssetHandle` existed, so it was
dealing with the file data directly. Now we want as little code as
possible to deal with the file data, all access should happen via the
`AssetHandle`.

source/blender/editors/asset/ED_asset_list.hh

@@ -34,5 +34,5 @@ std::string ED_assetlist_asset_filepath_get(const bContext *C,
                                             const AssetHandle &asset_handle);
 
 /* Can return false to stop iterating. */
-using AssetListIterFn = blender::FunctionRef<bool(FileDirEntry &)>;
+using AssetListIterFn = blender::FunctionRef<bool(AssetHandle)>;
 void ED_assetlist_iterate(const AssetLibraryReference *library_reference, AssetListIterFn fn);

source/blender/editors/asset/intern/asset_list.cc

@@ -215,7 +215,13 @@ void AssetList::iterate(AssetListIterFn fn) const
 
   for (int i = 0; i < numfiles; i++) {
     FileDirEntry *file = filelist_file(files, i);
-    if (!fn(*file)) {
+    if ((file->typeflag & FILE_TYPE_ASSET) == 0) {
+      continue;
+    }
+
+    AssetHandle asset_handle = {file};
+    if (!fn(asset_handle)) {
+      /* If the callback returns false, we stop iterating. */
       break;
     }
   }

source/blender/editors/interface/interface_template_asset_view.cc

@@ -170,11 +170,12 @@ static void asset_view_template_refresh_asset_collection(
 
   RNA_property_collection_clear(&assets_dataptr, assets_prop);
 
-  ED_assetlist_iterate(&asset_library, [&](FileDirEntry &file) {
+  ED_assetlist_iterate(&asset_library, [&](AssetHandle asset) {
     PointerRNA itemptr, fileptr;
     RNA_property_collection_add(&assets_dataptr, assets_prop, &itemptr);
 
-    RNA_pointer_create(nullptr, &RNA_FileSelectEntry, &file, &fileptr);
+    RNA_pointer_create(
+        nullptr, &RNA_FileSelectEntry, const_cast<FileDirEntry *>(asset.file_data), &fileptr);
     RNA_pointer_set(&itemptr, "file_data", fileptr);
 
     /* Copy name from file to asset-handle name ID-property. */