Describe the bug

The crosshair line for Line/Area charts is too light. There is an open discussion in EUI (elastic/eui#4308).

To Reproduce

1. Go to https://elastic.github.io/elastic-charts/?path=/story/line-chart--basic
2. Move the mouse over the line chart
3. The crosshair line is too light

Expected behaviour

The expected behaviour is that the line charts get the crosshair.line styles and right now it is getting the crosshair.band styles which are too light in color:

https://github.com/elastic/eui/blob/c0b8a25095e9fd60a5a9911d0cb1ba1249400ebf/src/themes/charts/themes.ts#L172-L181

Screenshots

Kibana Cross Issues

This issue was noticed while working on:
elastic/kibana#81565