convert coord btw. UTM and lat/lon

[yunjunz]

Description of proposed changes

• utils.utils0.py: add the following functions to convert coordinates between UTM and lat/lon, as described in https://github.com/insarlab/MintPy/discussions/1016#discussioncomment-6058402.

  • utm2latlon()
  • latlon2utm()
  • utm_zone2epsg_code(): bugfix if the latitude letter is not N or S
  • get_lat_lon(): convert UTM to lat/lon to ensure lat/lon output for hyp3 products. Together with #1050, this fixes #1049

• add utm to the dependency, since 1) it depends on numpy only; and 2) it's available on PyPI and conda-forge

  • requirements.txt
  • setup.py

Reminders

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• [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.
• [x] If adding new functionality, add a detailed description to the documentation and/or an example.