Add support for USGS 3DEP Seamless 1 m DEM (S1M)

[elidwa]

https://www.sciencebase.gov/catalog/item/67af83c1d34e5020fb91f170

USGS has begun publishing a new Seamless 1 m DEM (S1M) product under the 3DEP program. The data are stored in S3 at:

s3://prd-tnm/StagedProducts/Elevation/S1M/

Add a new Usgs3depS1meterDemRaster class (mirroring Usgs3dep10meterDemRaster).
Only Usgs3depS1meterDemRaster.h is needed.

[elidwa]

I started to implement it on branch: 3dep-seamless1m