Use Geometry rather than MultiPolygon for indexing records

[jodygarnett]

This is an experiment to try using Geometry (rather than MultiPolygon) in GeomUtils methods. Now that the index is no longer limited to MultiPolygons we should be able to work with any geometry content.

See previous discussion on #5396 with @fxprunayre

[jodygarnett]

@fxprunayre if you are happy with this to can replace #5396

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