RS_ZonalStats line rois: all_touched is ignored, and the default rule burns every traversed cell

[james-willis]

Probing RS_ZonalStats with LINESTRING rois on a 20x20 unit-pixel grid (the GH-3118 RasterizationTests fixtures) against GDAL/rasterio ground truth shows two line-specific behaviors in the rasterization path:

1. all_touched=true is ignored for line geometries. The count never changes with the flag; cells that the segment's envelope touches but does not cross are never included. GDAL/rasterio all_touched=True includes them.

   segment	default	all_touched (Sedona)	all_touched (GDAL/rasterio)
   LINESTRING (1.5 2.75, 10.5 7.25)	10	10	15
   LINESTRING (0.75 1.25, 4.25 11.75)	11	11	15
   LINESTRING (2.5 2.5, 9.5 9.5)	8	8	15

2. The default (no all_touched) line rule burns every traversed cell. GDAL's default line rasterization uses the centre/diamond crossing rule, which burns fewer: e.g. LINESTRING (1.3 2.7, 8.6 11.4) burns 17 cells in Sedona but 10 in GDAL/rasterio. (Corner-crossing segments mask this — their traversal and diamond counts coincide, which is why the Line rasterization uses fixed-step sampling instead of exact cell traversal, dropping boundary pixels (allTouched and LINESTRING) #3118 fixtures agree by default.)

Together these mean a line roi's zonal statistics differ from GDAL-based engines in both flag positions. Surfaced by the SedonaDB↔Sedona Spark parity suite (apache/sedona-db integration/spark-parity), where SedonaDB (GDAL rasterizer) matches rasterio in all four regimes.

GH-3118's direction-independence itself holds in every probed case (forward and reversed WKTs agree), as does the polygon path (the coastline fixture's pinned 1738/1842 counts match exactly).