ProjectExplorer: Use more FilePath in wizards, mostly JsonWizard*

JsonWizardFileGenerator's path member variables become FilePath and
GeneratedFile gets the QString based file setter and getter removed.

Also, a couple of other function parameters become FilePath. TODOs notes
added for further changes.

Change-Id: Ic4b791ed71c3c03adb8f15771e2dfa9af593abd8
Reviewed-by: <github-actions-qt-creator@cristianadam.eu>
Reviewed-by: hjk <hjk@qt.io>

src/plugins/projectexplorer/projectwizardpage.h

@@ -44,7 +44,7 @@ public:
     Core::IVersionControl *currentVersionControl();
 
     // Returns the common path
-    void setFiles(const QStringList &files);
+    void setFiles(const Utils::FilePaths &files);
 
     bool runVersionControl(const QList<Core::GeneratedFile> &files, QString *errorMessage);
 
@@ -75,7 +75,7 @@ private:
     Utils::TreeModel<> m_model;
 
     QList<Core::IVersionControl*> m_activeVersionControls;
-    QString m_commonDirectory;
+    Utils::FilePath m_commonDirectory;
     bool m_repositoryExists = false;
 
     QLabel *m_projectLabel;