Rebuild top-nav as LocalNav.

[cjcenizal]

Here's an audit I did of our other plugins' LocalNav components:

And here's an implementation of markup and styles for building these components: https://elastic.github.io/kibana-ui-framework/#/localnav

I think we will need to rebuild the top-nav directive (and the way it's configured) to accommodate our present and future use-cases. We'll need to think through how basic IA paradigms should work in our plugins (e.g. multi-leveled navigation, table views vs detail views, tabs, filters, searches, menu bars).

[cjcenizal]

Closed by #8679