In CppTools, keep cpp file settings in plugin and settings page
via shared pointer and apply to mime DB in
extensionsInitialized() (after CppEditor has loaded
and registered the mime types).

Task-number: 252299

replace ExtensionSystem::PluginManager::instance()->getObject<Core::ICore>() by Core::ICore::instance()

It is now possible to choose between case-sensitive or case-insensitive
completion. Also, you can now disable the automatic insertion of braces.

To match the class name, CppToolsPlugin.