TaskTree: Rename setupRoot into setRecipe

The passed Group root element is a recipe with
a full description on how to execute the tasks
and how to handle finished tasks.

We have already virtual methods / setters called like:
deployRecipe, refreshRecipe, reloadRecipe. So, the
common "recipe" is kind of consistent.

Fix typos in warnings.

Addresses the 11th point in the task below.

Task-number: QTCREATORBUG-28741
Change-Id: I1c80f4838b6a3e5ed113eaf8e42b59746d098efe
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: hjk <hjk@qt.io>
Reviewed-by: Marcus Tillmanns <marcus.tillmanns@qt.io>

src/plugins/diffeditor/diffeditorplugin.cpp

@@ -133,7 +133,7 @@ DiffFilesController::DiffFilesController(IDocument *document)
             tasks.append(AsyncTask<FileData>(std::bind(setupDiff, _1, inputList.at(i)),
                                          std::bind(onDiffDone, _1, i)));
         }
-        taskTree.setupRoot(tasks);
+        taskTree.setRecipe(tasks);
     };
     const auto onTreeDone = [this, storage] {
         const QList<std::optional<FileData>> &results = *storage;