Add highlighted vertical line to graph (with tooltip sticky to the line) (#6293)

* Add highlighted vertical line to graph

* Make tooltip stick to highlight line

* Format

* Update changelog

* Center tooltip over top if it fits neither left or right

* Clamp tooltip if it fits neither left or right

* Make it possible to drag on the chart to change selected period on mobile

* Fix edge case with tooltip flashing on L-shaped y pans

* Remove y position from state