LPS-34896 Show the global scope in the list of sites and enable site settings for it (limited to some options)
LPS-34898 Extend staging taglib to support contributing actions to an existing menu - Refactor logic into JSP
LPS-34898 Extend staging taglib to support contributing actions to an existing menu - Add new taglib param

I'm not 100% sure about the taglib param name (onlyActions) but I think that it's clear, specially consider that devs will be used to the old behavior of always rendering the menu.
LPS-34897 Move "staging" menu for global from the Control Panel menu to actions within sites administration
LPS-34896 Avoid showing the Global scope twice in the menu

This can only happen as of now for company admins since in that case it's returning an ArrayList and not a UniqueList, but I think it's better to have a more generic if clause. It is important to keep the logic to add the company group because for non company admins which certain permissions the getManageableGroups method does not account for all cases.