Vcs: Use PagedSettings for all plugin settings

Hopefully the last structural change for a while.

Settings lifetime is again tied to the plugin private.

Change-Id: I221e8b8baa69422306191b48a9f034ef5b1a0dc2
Reviewed-by: Orgad Shaneh <orgads@gmail.com>

src/plugins/git/gitplugin.cpp

@@ -397,6 +397,7 @@ public:
 
     void onApplySettings();
 
+    GitSettings setting;
     CommandLocator *m_commandLocator = nullptr;
 
     QAction *m_menuAction = nullptr;
@@ -433,8 +434,6 @@ public:
     std::unique_ptr<BlameMark> m_blameMark;
     QMetaObject::Connection m_blameCursorPosConn;
 
-    GitSettingsPage settingPage;
-
     GitGrep gitGrep{&m_gitClient};
 
     VcsEditorFactory svnLogEditorFactory {