Use from instead of name CLI flag for the tx sign cmd

[alexanderbez]

closes: #3711

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• Wrote tests

• Updated relevant documentation (docs/)

• Added entries in PENDING.md with issue #

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For Admin Use:

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[codecov]

Codecov Report

Merging #3713 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #3713   +/-   ##
========================================
  Coverage    61.15%   61.15%           
========================================
  Files          190      190           
  Lines        14008    14008           
========================================
  Hits          8567     8567           
  Misses        4905     4905           
  Partials       536      536

[cwgoes]

ACK

[alessio]

This should be an argument, not a flag.

[cwgoes]

This should be an argument, not a flag.

Maybe, I think it's nice to be explicit for key names though.