TaskTree: Rename TaskItem into GroupItem

Not all classes derived from TaskItem are tasks,
but the common denominator is that all may be placed
inside a group: thus GroupItem sounds more appropriate.

Addresses the 10th point in the bugreport below.

Task-number: QTCREATORBUG-28741
Change-Id: I94d728a8e39ec732810f2e5bbe6b9a76f3bc387c
Reviewed-by: Qt CI Patch Build Bot <ci_patchbuild_bot@qt.io>
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>

src/plugins/remotelinux/rsyncdeploystep.cpp

@@ -35,8 +35,8 @@ public:
 private:
     bool isDeploymentNecessary() const final;
     Group deployRecipe() final;
-    TaskItem mkdirTask();
-    TaskItem transferTask();
+    GroupItem mkdirTask();
+    GroupItem transferTask();
 
     mutable FilesToTransfer m_files;
     bool m_ignoreMissingFiles = false;
@@ -85,7 +85,7 @@ bool RsyncDeployStep::isDeploymentNecessary() const
     return !m_files.empty();
 }
 
-TaskItem RsyncDeployStep::mkdirTask()
+GroupItem RsyncDeployStep::mkdirTask()
 {
     const auto setupHandler = [this](Process &process) {
         QStringList remoteDirs;
@@ -113,7 +113,7 @@ TaskItem RsyncDeployStep::mkdirTask()
     return ProcessTask(setupHandler, {}, errorHandler);
 }
 
-TaskItem RsyncDeployStep::transferTask()
+GroupItem RsyncDeployStep::transferTask()
 {
     const auto setupHandler = [this](FileTransfer &transfer) {
         transfer.setTransferMethod(FileTransferMethod::Rsync);