running GDAL algorithms
If a subset string is set, we must export the subset of the layer
for use by the GDAL command*
Fixes#35981
* well, we probably **should** just build the gdal command to include
the SQL definition of the subset filter, but that's non-trivial, so
this fix is a good simple solution for now
Now GDAL algorithms test are splitted into parts: general tests, raster
algorithms and vector algorithms. This makes testing a bit faster and
easier, as there is no need to run not related tests.
