fix: polygon filter not working for point layers in GeoJSON column mode

[pierreeurope]

Summary

Polygon filter (draw-to-filter) doesn't work for point layers using GeoJSON column mode. Points inside the drawn polygon are not correctly filtered.

Root Cause

Two issues in geojsonPosAccessor in point-layer.ts:

1. Wrong data access pattern: When called from getPolygonFilterFunctor in filter-utils.ts, data is an object { index, dataContainer }, but the accessor treated it as an array (d[geojson.fieldIdx]), returning undefined.

2. No coordinate parsing: Even with correct data access, the accessor returned raw WKT strings (e.g. "POINT (7.63 45.04)") instead of [lng, lat] coordinates that isInPolygon expects.

Fix

• Curry geojsonPosAccessor with dataContainer (matching the pattern used by pointPosAccessor and geoarrowPosAccessor)
• Use dataContainer.valueAt() to properly access field values
• Parse WKT POINT strings into [lng, lat, alt] coordinate arrays
• Support GeoJSON objects with coordinates property
• Return [NaN, NaN, 0] for invalid/null data so the existing Number.isFinite check in filter-utils gracefully excludes them

Fixes #3278

[pierreeurope]

Note: I just noticed #3301 addresses the same issue. Apologies for the duplicate — I should have checked open PRs more carefully before submitting. Happy to close this in favor of #3301 if the maintainers prefer, or keep both open for comparison. The approaches differ slightly (this PR parses WKT in the accessor, while #3301 caches parsed results and supports MultiPoint).

[pierreeurope]

Closing in favor of #3321 which addresses the same issue with a more comprehensive approach.