Default to '*-DEM.tif' - do not assume out_dem_gsd

[dshean]

The default ASP output is outprefix-DEM.tif

Right now the asp_plot/stereo.py module assumes the DEM filename has format outprefix-DEM_{out_dem_gsd}m.tif or outprefix-{out_dem_gsd}m_DEM.tif

WARNING:asp_plot.utils:Could not find ('*-DEM_1m.tif', '*1m-DEM.tif') in WV02_20250131_103001010D1F0700_103001010DA86400/mgm_crop. Some plots may be missing.

Which results in a ValueError:

No DEM found in WV02_20250131_103001010D1F0700_103001010DA86400/mgm_crop with GSD 1 m. Please run stereo processing with the desired

This should not be the default. We should not assume they have an integer value and unit here.

A better option here might be to allow users to override the DEM filename.

[bpurinton]

A better option here might be to allow users to override the DEM filename.

I like this as an option. It's implemented now on #77