GPKG: do tile insertions by batch of 1000 in a transaction

git-svn-id: https://svn.osgeo.org/gdal/trunk@28167 f0d54148-0727-0410-94bb-9a71ac55c965
Remove unneeded FIXME

git-svn-id: https://svn.osgeo.org/gdal/trunk@28168 f0d54148-0727-0410-94bb-9a71ac55c965