feat: add bad debt query

[toteki]

Description

This query is something I wish I had when debugging umeemania liquidations - it will be useful in tracking the progress of bad debt repayment in situations where reserves are exhausted, and also provide a quick way to verify that repayment is working properly.

Note that when reserves are adequate and repayment is functioning, bad debts are repaid instantly in EndBlock, so the response will be empty most of the time.

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Author Checklist

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I have...

• included the correct type prefix in the PR title
• added ! to the type prefix if API or client breaking change
• added appropriate labels to the PR
• targeted the correct branch (see PR Targeting)
• provided a link to the relevant issue or specification
• added a changelog entry to CHANGELOG.md
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Reviewers Checklist

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• confirmed the correct type prefix in the PR title
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• reviewed state machine logic
• reviewed API design and naming
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• reviewed tests and test coverage
• manually tested (if applicable)

[codecov-commenter]

Codecov Report

Merging #1238 (a63a3bb) into main (8277b19) will decrease coverage by 0.42%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #1238      +/-   ##
==========================================
- Coverage   50.95%   50.53%   -0.43%     
==========================================
  Files          67       67              
  Lines        6774     6831      +57     
==========================================
  Hits         3452     3452              
- Misses       3078     3135      +57     
  Partials      244      244              

Impacted Files	Coverage Δ
x/leverage/keeper/grpc_query.go	60.69% <0.00%> (-2.95%)	⬇️
x/leverage/types/query.pb.gw.go	0.00% <0.00%> (ø)