Fix gaps in gainmap support in TransformationUtils

We need to update the remainder of TransformationUtils (i.e., not rotateImageExif which was handled in https://github.com/bumptech/glide/issues/5333) to remove usage of BitmapPool and use Bitmap.create to create Bitmaps. See https://github.com/bumptech/glide/pull/5334/ for an example of how to do it.

Start by reading TransformationUtils and the example in pull request #5334, while noting that rotateImageExif was handled separately in issue #5333. Update the remaining gainmap-related paths to stop using BitmapPool and create Bitmaps with Bitmap.create; done means the remainder follows the example without changing rotateImageExif.

Written by the indexing model from the issue text.