[#140] use with-utf8 library to handle encoding issues

Description

There is a new library developed by Serokell which is supposed to help you do the right thing dealing with encodings: https://hackage.haskell.org/package/with-utf8

We have some utilities (e. g. see Util.IO) that are present in that library. We are already trying to do the right thing, but apparently it's done not quite consistently across our executables. Also since this functionality is extracted into a library with a specific purpose, it certainly makes sense to use that library.

Related issue(s)

Resolves #140 (closed)

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