feat: (x/bank) add SpendableCoin method to BaseViewKeeper

[hallazzang]

Description

Closes: #12570

• Implement SpendableCoin method
• Write unit tests
• Add gRPC query (Not needed)
• Update relevant docs

This PR adds SpendableCoin method to the bank module's BaseViewKeeper.

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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
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• followed the guidelines for building modules
• included the necessary unit and integration tests
• added a changelog entry to CHANGELOG.md
• included comments for documenting Go code
• updated the relevant documentation or specification
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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
• reviewed documentation is accurate
• reviewed tests and test coverage
• manually tested (if applicable)

[alexanderbez]

@hallazzang I'm not really sure we need a gRPC query for this. We already have one for spendable coins. Maybe we can just add a query param to that one to filter by a single denom. No need for a whole new query.

[hallazzang]

@alexanderbez Oh, I see. I agree with you. I'll finish the other tasks then.

[julienrbrt]

Can we add a changelog? :)

[hallazzang]

@julienrbrt Sure. I've updated the CHANGELOG file and also merged main into this branch.

[julienrbrt]

lgtm!

[codecov]

Codecov Report

Merging #12593 (78867bb) into main (818da70) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main   #12593   +/-   ##
=======================================
  Coverage   65.19%   65.19%           
=======================================
  Files         693      693           
  Lines       71802    71806    +4     
=======================================
+ Hits        46809    46812    +3     
- Misses      22359    22360    +1     
  Partials     2634     2634           

Impacted Files	Coverage Δ
x/bank/keeper/view.go	83.87% <100.00%> (+0.53%)	⬆️
crypto/keys/internal/ecdsa/privkey.go	81.13% <0.00%> (-1.89%)	⬇️