Fix 0.39 x/auth Migration Types

[alexanderbez]

Description

Ref: #6829

Forgot to add Coins to JSON output. Added migration tests.

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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 #6870 into master will increase coverage by 0.01%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #6870      +/-   ##
==========================================
+ Coverage   61.29%   61.31%   +0.01%     
==========================================
  Files         510      511       +1     
  Lines       31635    31648      +13     
==========================================
+ Hits        19392    19405      +13     
  Misses      10727    10727              
  Partials     1516     1516              

[anilcse]

utACK