New workload: geoshape (OpenStreetMap polygons and linestrings)

Port the OSB `geoshape` workload. PlanetOSM linestrings, multilinestrings, and polygons in WKT format (Open Database Licence). Exercises Solr's `SpatialRecursivePrefixTreeFieldType` / JTS with intersects, contains, and within predicates — not covered by any current workload.

## Tasks
- Convert OSB workload using `solr-orbit convert-workload`
- Map WKT geometry field to Solr `location_rpt` field type
- Define operations: intersects, contains, within polygon queries
- Add 1k sample corpus for test-mode
- Check whether any operations belong in `common_operations/` rather than this workload

**Depends on:** #3 (ASF dataset hosting must be resolved before corpus files can be finalised)

## References
- OSB workload: https://github.com/opensearch-project/opensearch-benchmark-workloads/tree/main/geoshape
- Creating workloads: https://github.com/apache/solr-orbit/blob/main/CREATE_WORKLOAD_GUIDE.md