Utils: Introduce a FilePath constructor from char arrays

Similar to QT_RESTRICTED_CAST_FROM_ASCII to avoid the need for
decorations in user code.

At the same time, drop some convenience constructors and functions
in CommandLine and Icon essentially serving the same purpose.

Change-Id: Ida4e5ac19c2da0a4298a97b2a8e1511d56bbb79d
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/plugins/cmakeprojectmanager/cmakebuildsystem.cpp

@@ -755,7 +755,7 @@ void CMakeBuildSystem::handleParsingSucceeded()
         checkAndReportError(errorMessage);
     }
 
-    m_ctestPath = m_reader.ctestPath();
+    m_ctestPath = FilePath::fromString(m_reader.ctestPath());
 
     setApplicationTargets(appTargets());
     setDeploymentData(deploymentData());