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

Reminders

• [x] Pass Pre-commit check (green)
• [x] Pass Codacy code review (green)
• [x] Pass Circle CI test (green)
• [x] Make sure that your code follows our style. Use the other functions/files as a basis.
• [x] If modifying functionality, describe changes to function behavior and arguments in a comment below the function declaration.