readfile: support Gamma SLC in complex32 format

[yunjunz]

Description of proposed changes

• utils.readfile: support Gamma slc in complex32 format

  • add scomplex to complex32 data type conversion
  • read_binary_file(): support .rslc/rmli file extension
  • read_complex_int16(): refactor to use cpx_band in str for a more flexible output data; revise the output from 2 matrices into 1 matrix
  • read_binary(): support complex32 while calling read_complex_int16(), since it's not supported in numpy.

• utils.readfile.auto_no_data_value(): add geometrical offset files from alos2App with num of band = 1

• view.viewer.plot(): set pixels with no data value to np.nan, instead of call np.ma.masked_where(), which seems over-complicated (compared with setting to nan) and I could not recall the reason anymore.

• cli/prep_isce.py: set -f default from str to list, to be consistent with the non-default var type.

Reminders

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

[yunjunz]

Local testing passed without issue. The failed circle CI test shows that GDAL can not be imported, but it's installed during the installation process. Nevertheless, the circle CI error is not related with the PR, and probably due to some issue on circle CI itself.