resample: refactor default output step size calculation

[yunjunz]

Description of proposed changes

• rename utils.utils0.auto_lat_lon_step_size() to objects.resample.resample.get_lat_lon_step()

  • move the location because this function is only used in the resample code so far
  • add the user-specified lalo_step code body into this function, for a more simple prepare_geometry_definition_radar()
  • replace try/except with if/else and explicit required metadata checking and warning msg

• objects.resample.resample.prepare_geometry_definition_radar.find_valid_lat_lon():

  • rename mark_lat_lon_anomaly() to find_valid_lat_lon()
  • add more comments on the input/output args

• cli.geocode: set default fillValue to zero for .int/unw files, to be consistent with isce/roipac.

• docs/api/module_hierarchy.md: update for objects.resample.py

• objects.progress.FileProgressObject(): display in int MB to be simple

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