TimeSeries: improve tooltip cursor proximity tracking on both axes

### What happened? When hovering the mouse near a data point in a time series panel, the point is high lighted (see green shadow around green data point in the image). But instead of showing the data that belongs to the highlighted point, it seems the data belonging to the data point that is nearest in the up/down dimension is shown in the overlay (dark red instead of green). It is really hard to get the data for the nearest point in this case.  ### What did you expect to happen? Show data belonging to highlightest nearest (in x and y dimension) data point in overlay. Also I would expect only one data point to be highlighted at a time..it seems many data points are selected ### Did this work before? no idea ### How do we reproduce it? 1. create data set as shown in the image (many close by points in up down dimension but with good difference in left/right dimension) 2. hover mouse near data point 3. observe data overlay ### Is the bug inside a dashboard panel? _No response_ ### Environment (with versions)? Grafana: Grafana v11.0.0 (83b9528bce) OS: win10 Browser: chrome 125.0.6422.142 ### Grafana platform? I don't know ### Datasource(s)? influxdb via flux