x/slashing: In-Process CLI Integration Tests

[alexanderbez]

Description

ref: #6423

Note, there were bugs in some of the Proto schemas WRT to JSON and YAML tags, which I fixed.

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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 #6702 into master will increase coverage by 0.86%.
The diff coverage is 41.37%.

@@            Coverage Diff             @@
##           master    #6702      +/-   ##
==========================================
+ Coverage   57.68%   58.54%   +0.86%     
==========================================
  Files          94      511     +417     
  Lines        6217    30981   +24764     
==========================================
+ Hits         3586    18139   +14553     
- Misses       2466    11495    +9029     
- Partials      165     1347    +1182