feat!: add testnet cmd

[aleem1314]

Description

Closes: #563
Ref: #9246

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[codecov]

Codecov Report

Merging #607 (c937a3e) into master (05dfaec) will increase coverage by 1.26%.
The diff coverage is 24.26%.

❗ Current head c937a3e differs from pull request most recent head c445e0d. Consider uploading reports for the commit c445e0d to get more accurate results

@@            Coverage Diff             @@
##           master     #607      +/-   ##
==========================================
+ Coverage   74.09%   75.35%   +1.26%     
==========================================
  Files         104      104              
  Lines       14899    14271     -628     
==========================================
- Hits        11039    10754     -285     
+ Misses       3131     2823     -308     
+ Partials      729      694      -35     

Flag	Coverage Δ
experimental-codecov	75.35% <24.26%> (+1.26%)	⬆️
stable-codecov	66.91% <21.96%> (?)

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[ryanchristo]

tACK. Cross-referenced with the implementation in cosmos-sdk. Looks good! The only request would be to be to add .testnets to .gitignore but pre-approving.

Also, one issue with running make localnet-start but unrelated to the implementation. It seems to be an issue using the latest libc, which is available on Ubuntu 21.10.