CMake: Simplify based on Project::projectFileIsDirty signal

Delegate all the necessary file watching to Project and connect
to the relevant signal.

Server-mode insists on watching files itself, so that may not
report extra project files.

Change-Id: If821c54a7b0f8b72beed53dd1c83f255973faf3e
Reviewed-by: hjk <hjk@qt.io>

src/plugins/cmakeprojectmanager/fileapireader.cpp

@@ -175,6 +175,11 @@ bool FileApiReader::isParsing() const
     return m_isParsing;
 }
 
+QVector<FilePath> FileApiReader::takeProjectFilesToWatch()
+{
+    return QVector<FilePath>::fromList(m_cmakeFiles.toList());
+}
+
 QList<CMakeBuildTarget> FileApiReader::takeBuildTargets(QString &errorMessage){
     Q_UNUSED(errorMessage)