Move Geo settings from Settings -> Geo to Geo -> Settings

Summary

Currently the settings page of Geo lives in Admin Area -> Settings -> Geo. According to the conversation in gitlab-foss#66034 (comment 204977904), it should change to Admin Area -> Geo -> Settings.

Geo -> Nodes	Geo -> Settings

During the transition

In order to avoid confusion by the user around these changes, we are going to keep the page at Settings -> Geo in the navigation for 4-5 milestones, but automatically redirect the user to Geo -> Settings. If we combine this with an alert at the top of the page, this could be a rather clean and more direct option with enough information for the user to understand the upcoming changes.