Problem description: If the user, that uses keyboard navigation, opens the SVG graph pop-up hintbox (clicks on any data point on a Graph (new) widget) the focus is able to move away from the hintbox, and the user can navigate to any other field keeping the pop-up hintbox open. If such pop-up is open and keyboard navigation is used, it should be possible to navigate only inside the pop-up until ti's closed.

Steps to reproduce:
1. Navigate to Monitoring => Dashboard
2. Open an existing Dashboard (or create a new one)
3. Create a "Graph" widget.
4. Save the widget and the dashboard.
5. Click on any data point in the created graph widget - a pop-up hintbox with detailed values that this point represents should appear.

Result 1: Focus of keyboard navigation is outside of the pop-up hintbox.
Expected: Focus should be on the "Close" button of this pop-up hintbox.

6. Get the focus of keyboard navigation on the "Close" button of the SVG graph pop-up hintbox and attemt to navigate away without closing the pop-up.

Result 2: It is possible to get the focus of the pop-up hintbox without closing the pop-up.
Expected: When a popup is open, it should be possible to navigate only inside of it. After popup is closed, focus should be returned to the element, that opened this popup.