fix: add overflow checking and test codes for cover edge cases

[dongsam]

Description

closes: #457

---

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 #458 (d6be8a6) into develop (616985f) will increase coverage by 0.39%.
The diff coverage is 88.63%.

❗ Current head d6be8a6 differs from pull request most recent head 59d7de7. Consider uploading reports for the commit 59d7de7 to get more accurate results

@@             Coverage Diff             @@
##           develop     #458      +/-   ##
===========================================
+ Coverage    85.09%   85.49%   +0.39%     
===========================================
  Files           23       23              
  Lines         2604     2634      +30     
===========================================
+ Hits          2216     2252      +36     
+ Misses         225      221       -4     
+ Partials       163      161       -2     

Impacted Files	Coverage Δ
x/liquidity/keeper/swap.go	62.92% <25.00%> (-1.45%)	⬇️
x/liquidity/keeper/liquidity_pool.go	84.62% <87.50%> (+1.46%)	⬆️
x/liquidity/keeper/batch.go	89.15% <100.00%> (+0.33%)	⬆️
x/liquidity/types/swap.go	79.22% <100.00%> (+0.11%)	⬆️
x/liquidity/types/utils.go	89.06% <100.00%> (+3.64%)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 616985f...59d7de7. Read the comment docs.