[GH-2652] Add RS_AsCOG SQL function for Cloud Optimized GeoTiff output

[jiayuasu]

Did you read the Contributor Guide?

• Yes, I have read the Contributor Rules and Contributor Development Guide

Is this PR related to a ticket?

• Yes, and the PR name follows the format [GH-XXX] my subject. Closes Add RS_AsCOG (Cloud Optimized GeoTiff) writer with necessary configs #2652

What changes were proposed in this PR?

This PR adds the RS_AsCOG SQL function that converts a raster to a Cloud Optimized GeoTIFF (COG) byte array. The underlying pure Java COG writer was already merged via #2663 (sub-issue #2662). This PR wires it up as a Spark SQL function with positional overloads:

RS_AsCOG(raster)
RS_AsCOG(raster, compression)
RS_AsCOG(raster, compression, tileSize)
RS_AsCOG(raster, compression, tileSize, quality)
RS_AsCOG(raster, compression, tileSize, quality, resampling)
RS_AsCOG(raster, compression, tileSize, quality, resampling, overviewCount)

Parameters:

• compression: Deflate (default), LZW, JPEG, PackBits
• tileSize: Tile width/height in pixels, must be a power of 2 (default 256)
• quality: Compression quality from 0.0 (max compression) to 1.0 (default 0.2)
• resampling: Overview resampling algorithm - Nearest (default), Bilinear, Bicubic
• overviewCount: Number of overview levels, -1 for auto (default), 0 for none

Files changed:

• common/.../raster/RasterOutputs.java - 6 positional asCOG Java overloads
• spark/.../expressions/raster/RasterOutputs.scala - RS_AsCOG Spark SQL expression
• spark/.../UDF/Catalog.scala - Function registration
• common/.../raster/RasterOutputTest.java - 8 Java unit tests including round-trip
• spark/.../sql/rasteralgebraTest.scala - 5 Spark integration tests including round-trip
• docs/api/sql/Raster-writer.md - RS_AsCOG API reference documentation
• docs/tutorial/raster.md - Added COG section to raster tutorial

How was this patch tested?

• 8 Java unit tests in RasterOutputTest covering all overloads and a GeoTiff round-trip (read GeoTiff, write COG, read back, verify envelope, dimensions, and band count)
• 5 Spark SQL integration tests in rasteralgebraTest covering defaults, compression variants, tile size, all arguments, and a round-trip through RS_FromGeoTiff(RS_AsCOG(raster))
• All tests pass locally

Did this PR include necessary documentation updates?

• Yes, added RS_AsCOG section to the Raster writer API docs (docs/api/sql/Raster-writer.md) with full parameter descriptions, format signatures, SQL examples, and output schema
• Added a Cloud Optimized GeoTiff section to the raster tutorial (docs/tutorial/raster.md)