fix(tooltip): handle multiple points (#979)

[jernestmyers]

🐛 Bug Fix

Relates to #979

Adds an optional prop (findNearestDatumOverride) to the XYChart and GlyphSeries components that get passed into the useEventHandlers hook for improved tooltip behavior. This felt like a viable path given that the useEventHandlers hook already includes the following prop definition:

  /** Optionally override the findNearestDatum logic. */
  findNearestDatum?: (
    params: NearestDatumArgs<XScale, YScale, Datum>,
  ) => NearestDatumReturnType<Datum>;

I tested this approach in a new viz component we are building and the tooltip behaves as desired/expected by using findNearestDatumXY as the override function when consuming XYChart and GlyphSeries.

Happy to improve upon this implementation or open to alternatives.

[owenbirdsall]

This looks good to me, it would be really helpful if this could be merged in as I imagine it's quite common to want to have multiple points occupying the same x location with varying y locations.