Resample Copernicus DEM tiles to unified width

[kautlenbachs]

There is an issue with SNAP inherited logic - https://forum.step.esa.int/t/copernicus-dem-complications-when-coregistering-s1/38659/2

Biggest issue is coregistering reference and secondary scenes' pixels.

Solution for this would be to resample all the tiles to the same width.

[kautlenbachs]

Wiki page dedicated to this - https://github.com/cgi-estonia-space/ALUs/wiki/DEM-handling-functionality-for-Sentinel-1-processors

[kautlenbachs]

Seems like blatantly resampling DEM is very okay to do:

• https://pyrosar.readthedocs.io/en/latest/general/DEM.html#dem-mosaicing
• https://senbox.atlassian.net/browse/SNAP-3471