[Inspector] Use tabs for view selection

The current view selection interface for Lens' inspect flyout is currently less-than-ideal. The view selection currently uses a combination of a button and subsequent popover. Interacting with this requires two clicks from a user in order to switch views, even though the popover only contains two options. Additionally, the placement of the button doesn’t look great, with the button being in such close proximity to the offset close flyout button.

I’d like to suggest that we change the button/popover to instead be a set of tabs that appear below the “Inspector” heading. This will better expose the view options to users, allow them to quickly change with a single click, and also likely look better.

CCing @andrewctate, as he was the one that kindly brought this to my attention.