More CLI cleanup

[alexanderbez]

Description

• Improve gentx UX.
• Remove default directory args.
• Allow moniker to be provided.

---

Before we can merge this PR, please make sure that all the following items have been
checked off. If any of the checklist items are not applicable, please leave them but
write a little note why.

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Linked to Github issue with discussion and accepted design OR link to spec that describes this work.
• Code follows the module structure standards.
• Wrote unit and integration tests
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added relevant godoc comments.
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer
• Review Codecov Report in the comment section below once CI passes

[codecov]

Codecov Report

Merging #6651 into master will increase coverage by 1.12%.
The diff coverage is 9.52%.

@@            Coverage Diff             @@
##           master    #6651      +/-   ##
==========================================
+ Coverage   56.45%   57.58%   +1.12%     
==========================================
  Files         412      500      +88     
  Lines       24503    29999    +5496     
==========================================
+ Hits        13834    17275    +3441     
- Misses       9578    11479    +1901     
- Partials     1091     1245     +154     

[fedekunze]

ACK. Pending changelog entry for genutil changes