GPKG: avoid temporary filename collision issue when a ReadTile() causes a WriteTile() due to cache saturation, and also fix color table expansion on partial tile to avoid 'ghost' content in the transparent area

git-svn-id: https://svn.osgeo.org/gdal/trunk@28075 f0d54148-0727-0410-94bb-9a71ac55c965
RasterIO: small optimization in generic RasterIO() implementation to avoid loading partial tiles at right and/or bottom edges of the raster when they are going to be completely written 

git-svn-id: https://svn.osgeo.org/gdal/trunk@28076 f0d54148-0727-0410-94bb-9a71ac55c965
Improve error message

git-svn-id: https://svn.osgeo.org/gdal/trunk@28077 f0d54148-0727-0410-94bb-9a71ac55c965
Merge branch 'trunk' into trunk_travis_macosx