ClangTools: Move run settings to projects mode

Make the global run settings available per project in project mode and
thus remove the diagnostic config selection from the
selectable-files-dialog:

 * Extract the classes RunSettings and RunSettingsWidget instead of
   duplicating stuff.
 * Ensure to pick up the old settings
 * Add some convenience buttons/links in projects mode allowing to
   restore the global settings, to open the global settings and to
   navigate (back) to the analyzer mode.

Change-Id: I1b91b6f8e58a87a025774e4643c46e176b2a8885
Reviewed-by: Cristian Adam <cristian.adam@qt.io>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@qt.io>

src/plugins/clangtools/settingswidget.h

@@ -43,6 +43,9 @@ class SettingsWidget : public QWidget
 public:
     SettingsWidget(ClangToolsSettings *settings, QWidget *parent = nullptr);
     ~SettingsWidget() override;
+
+    void apply();
+
 private:
     std::unique_ptr<Ui::SettingsWidget> m_ui;
     ClangToolsSettings *m_settings;