HorizontalAxis: Add label-alignment customization

[patrykandpatrickbot]

In particular, extreme labels should be shiftable inward. See #394 and #594.

[claude[bot]]

Implemented in 3.3.0.

HorizontalAxis.ItemPlacer gains getShiftExtremeLabels, and HorizontalAxis.ItemPlacer.aligned gains a matching shiftExtremeLabels parameter. When enabled, the first and last labels are end-aligned and start-aligned rather than centered on their x positions, anchoring them to the plot-area edges. This prevents clipping without shrinking the plot area, unlike addExtremeLabelPadding; where both are enabled, shiftExtremeLabels takes precedence.

A new HorizontalAxis.ItemPlacer.extremes places labels, ticks, and guidelines only at the first and last x values, with the same alignment.

bottomAxis =
  HorizontalAxis.rememberBottom(
    itemPlacer = remember { HorizontalAxis.ItemPlacer.aligned(shiftExtremeLabels = true) }
  )

This covers the extreme-label case from #394 and #594, which is what this thread was opened for. Broader per-label alignment customization isn’t included; if there’s a concrete use case for it, a separate thread is the place for it.

_{Based on maintainer input.}