ProjectExplorer: Shorten space needed to store a FileType

Use class enum to shorten the FileType to quint16. This frees up a couple
of bytes per FileNode and we can have many of those.

Change-Id: I3a9ae25059690fefa15305a4268269647d6dc1c9
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/nim/project/nimproject.cpp

@@ -110,7 +110,7 @@ void NimProject::collectProjectFiles()
         m_futureInterface.reportStarted();
         QList<FileNode *> nodes
                 = FileNode::scanForFiles(projectDirectory(),
-                                         [](const FileName &fn) { return new FileNode(fn, SourceType, false); },
+                                         [](const FileName &fn) { return new FileNode(fn, FileType::Source, false); },
                                          &m_futureInterface);
         m_futureInterface.setProgressValue(m_futureInterface.progressMaximum());
         m_futureInterface.reportResult(nodes);