Add support for core Navigation Top Bar

Front end is not my expertise, but I felt like rather than completely overriding the gin template, just using the `form_actions` variable already defined intop-bar--gin.html.twig would make it easier to support. This branch fixes functionality issues but still needs styling fixes.

I pushed some styling fixes that seem to be working pretty well on desktop at least..

Looking into it more, we'd probably want to remove the dependency for gin_toolbar and core's toolbar and instead would want to conditionally work based on what modules exist on the given site. Definitely needs more work and maybe some guidance from maintainers.

Hi,

Thanks for your work on this issue.

I would wait to see how Gin will handle the new Navigation module. If some cases are deprecated like, now every one has a vertical toolbar, etc.

But having optional stuff for people no more using admin_toolbar and gin_toolbar would be very nice.