Incorrect implementation of `scaleXTime()`/`scaleYTime()` "time delta" scales

Let's plot allows an axis to be scaled as a continuous time delta or "duration".
I currently cannot find a way to easily plot a `Duration` like a number of hours/days/minutes etc.

For example:
https://nbviewer.org/github/JetBrains/lets-plot-kotlin/blob/master/docs/examples/jupyter-notebooks/scale_time.ipynb

from: https://github.com/JetBrains/lets-plot-kotlin/blob/master/plot-api/src/commonMain/kotlin/org/jetbrains/letsPlot/scale/DateTime.kt

Start with plot-api/src/commonMain/kotlin/org/jetbrains/letsPlot/scale/DateTime.kt and compare scaleXTime()/scaleYTime() with the scale_time.ipynb example linked in the issue. Determine how duration values are currently handled and verify the corrected behavior by plotting durations expressed as hours, days, or minutes.

Written by the indexing model from the issue text.