gs:DownloadEstimator should check size is less than Integer.MAX_VALUE

The gsownloadEstimator process only checks the requested size against the configured raster size limit, without worrying to check that it is also a valid Integer value.

If one raises the raster size limit above Integer.MAX_VALUE in the configuration and tries to download a huge image (e.g. 100,000 * 60,000), the estimator will say the request is ok, but the actual download will throw an exception:

At the very least, the estimator should return false if the requested image size is above Integer.MAX_VALUE.