Detailed analytics for every widget

Each widget now has its own analytics page, opened from the Analytics page.

• A header with the widget name and type, so you know which placement you are looking at.
• A device filter that updates every card on the page.
• Impressions by device, watch time by surface and video completion rate.
• A per-video breakdown, including each video's tagged products.
• Influenced and direct revenue for the widget.

Each card loads on its own, so the charts no longer wait for the video table.