Context help for various views doesn't work if code view is closed

A lot of views request context sensitive help via QmlDesignerPlugin::contextHelp(), which ultimately ends up calling "m_widget->textEditor()->contextHelp(callback)" in TextEditorView. However, with DETACH_DISABLED_VIEWS, this only works if code view is open.

It also looks like context help in general needs some fixing in project storage builds, judging from code comment and ifdeffing on TextEditorView::qmlJSEditorContextHelp.

For example:

• Create new empty project
• Close all views except navigator
• Select the root node of scene
• Press f1 for context help

--> Nothing happens.

• Open code view
• Select root node of the scene
• Press f1 for context help

--> Context help opens