SQLServerSpatial Provider: improve geometries fetching performance

[danstoica]

Currently when a larger than 5K geometry is hit, the geometries are unbound and all the subsequent batches are fetched as blobs. Note array fetch mechanism is in place.

This can be optimezed as:

• enlarge the buffer size (say 10K)
• fetch as blob only the truncated geometry
• rebind back the array of geometries.