Add `DataColumn` API for breaks in `Legend`/`Axis`

Add new `breaks` (an analogue for all existing function) with `DatColumn` argument for passing breaks for axis and legend:

`fun breaks(breaks: DataColumn, format: String? = null)`

https://github.com/Kotlin/kandy/blob/main/kandy-lets-plot/src/main/kotlin/org/jetbrains/kotlinx/kandy/letsplot/scales/guide/model/LetsPlotAxis.kt
https://github.com/Kotlin/kandy/blob/main/kandy-lets-plot/src/main/kotlin/org/jetbrains/kotlinx/kandy/letsplot/scales/guide/model/LetsPlotLegend.kt
A common case:
```
legends {
breaks(column.distinct())
}
```

Start with the existing breaks APIs in LetsPlotAxis.kt and LetsPlotLegend.kt, then compare their signatures with the requested DataColumn overload. Trace how the legends { breaks(column.distinct()) } example should reach both guide models. Done means both APIs accept DataColumn values with the optional format and preserve the existing breaks behavior.

Written by the indexing model from the issue text.