Fix ParquetProvider geometry handling and add configurable geometry column support

[MatthewDownsNR]

Overview

This PR enhances the ParquetProvider with critical geometry handling fixes and adds support for configurable geometry columns, including WKT format support.

Key improvements:

• Fixed critical index mismatch bug that caused geometry to appear as null in individual item requests (/collections/.../items/[id])
• Added support for configurable geometry columns via geometry_column parameter in provider configuration
• Added WKT (Well-Known Text) geometry support alongside existing WKB support
• Enhanced geometry source prioritization with proper fallback handling
• Improved error handling and logging for geometry operations
• Added backward compatibility for older pygeoapi versions without crs_transform

Bug fixes:

• Resolved 'list' object attribute 'index' is read-only error in get() method
• Fixed geometry index alignment issues in both query() and get() methods
• Corrected bbox filtering logic for x/y field configurations

Related Issue / discussion

This PR addresses multiple issues reported by users:

• Parquet files with existing geometry columns (WKT format) were not supported
• Individual item requests returned null geometry despite having valid geometry data
• Users experienced "identifier not found" errors due to geometry processing failures
• The provider only supported x/y coordinate fields, not pre-existing geometry columns

These improvements make the ParquetProvider more robust and compatible with real-world geospatial parquet files that contain geometry in various formats.

Additional information

Testing performed:

• All existing 12 ParquetProvider tests continue to pass
• Added comprehensive testing for WKT geometry column support
• Verified backward compatibility with x/y field configurations
• Tested with both S3 and local file sources
• Confirmed proper handling of missing geometry scenarios

Configuration examples:

# New geometry column support
providers:
  - type: feature
    name: Parquet
    data:
      source: s3://bucket/data.parquet
    geometry_column: wkt_geom  # Now supported!
    id_field: unique_id

# Existing x/y field support (unchanged)
providers:  
  - type: feature
    name: Parquet
    data:
      source: local_data.parquet
    x_field: longitude
    y_field: latitude
    id_field: id

Breaking changes: None - all changes are backward compatible.

Dependency policy (RFC2)

• I have ensured that this PR meets RFC2 requirements

Updates to public demo

• I have ensured that breaking changes to the pygeoapi master demo server have been addressed
  • https://github.com/geopython/demo.pygeoapi.io/blob/master/services/pygeoapi_master/local.config.yml

Note: No breaking changes were introduced, so no demo updates are required.

Contributions and licensing

(as per https://github.com/geopython/pygeoapi/blob/master/CONTRIBUTING.md#contributions-and-licensing)

• I'd like to contribute bugfix and feature enhancements to pygeoapi. I confirm that my contributions to pygeoapi will be compatible with the pygeoapi license guidelines at the time of contribution
• I have already previously agreed to the pygeoapi Contributions and Licensing Guidelines