State Timeline: Add "Tooltip: Hover Proximity" setting.

<!-- Please only use this template for submitting feature requests --> **Why is this needed**: Hover proximity is helpful on Time Series & Trend visualizations because it is hard to hover over a point. This also applies to very short events that produce a very narrow box in a State Timeline viz; it can be very difficult to see the tooltip for a very short event, e.g. a 1-second State event on a 14-day time range. **What would you like to be added**: Add "Tooltip - Hover proximity" setting to the State Timeline visualization, primarily for the left-to-right position of the mouse. **Who is this feature for?** Any user of State Timeline that has events of varying length on a long enough time frame. In the image below, you can see the dashed line showing where the mouse was hovering, trying to show the tooltip for the purple event in the middle of the visualization. <img width="1540" height="567" alt="Image" src="https://github.com/user-attachments/assets/ab37c043-0b4c-45f3-8081-d0563b44033b" />