ProjectExplorer: Merge IDevice::{filePath,mapToGlobalPath}

They were doing practically the same. Keep the 'filePath' name for
now until something more fitting comes up.

Change-Id: I96ca4da4b30b7b463583e002f2c19d6e6c5541e6
Reviewed-by: Jarek Kobus <jaroslaw.kobus@qt.io>

src/plugins/docker/dockerdevicewidget.cpp

@@ -167,7 +167,7 @@ DockerDeviceWidget::DockerDeviceWidget(const IDevice::Ptr &device)
                 paths.append(FilePath::fromString(path.trimmed()));
         }
         paths = Utils::transform(paths, [dockerDevice](const FilePath &path) {
-            return dockerDevice->mapToGlobalPath(path);
+            return dockerDevice->filePath(path.path());
         });
         return paths;
     };