add support for gdalraster?

[njtierney]

https://github.com/USDAForestService/gdalraster

[brownag]

There are two main ways that we can support or use gdalraster in geotargets.

The first way would be to add support for gdalraster objects i.e. GDALRaster and future GDALVector. These are C++ classes that are similar to terra objects in that they have a pointer that cannot be serialized and thus suffer from the same issues in targets that we seek to resolve with this package.

A second way we can incorporate this package would be to use some of the GDAL API that is exposed in gdalraster but not (yet) available in terra methods. For example, gdalraster::addFilesInZip() can be used to create or append to SOZip files. Example of this is given in #123