test: add validation & unit tests in fswap module

[170210]

Description

closes: #XXXX

Motivation and context

How has this been tested?

Screenshots (if appropriate):

Checklist:

• I followed the contributing guidelines and code of conduct.
• I have added a relevant changelog to CHANGELOG.md
• I have added tests to cover my changes.
• I have updated the documentation accordingly.
• I have updated API documentation client/docs/swagger-ui/swagger.yaml

[170210]

Is it necessary to add the following validate in validateBasic:

• Whether Swaps[0].AmountCapForToDenom is greater than Swappeds[0].ToDenom.Amount
  

  finschia-sdk/x/fswap/types/genesis.go

  Lines 59 to 60 in 8e14cdb

  	if swap.AmountCapForToDenom.LT(swapped.ToCoinAmount.Amount) {
  	return ErrInvalidState.Wrap("AmountCapForToDenom cannot be exceeded")

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.68%. Comparing base (92ad675) to head (1f01fc9).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1382      +/-   ##
==========================================
+ Coverage   69.58%   69.68%   +0.10%     
==========================================
  Files         668      668              
  Lines       56231    56242      +11     
==========================================
+ Hits        39126    39194      +68     
+ Misses      14834    14775      -59     
- Partials     2271     2273       +2     

Files	Coverage Δ
simapp/app.go	80.00% <100.00%> (ø)
x/fswap/keeper/keeper.go	60.16% <100.00%> (+9.30%)	⬆️
x/fswap/types/genesis.go	81.25% <100.00%> (+53.25%)	⬆️

... and 3 files with indirect coverage changes

[jaeseung-bae]

Can you check failed test in CI?

[zemyblue]

How about adding unvalidated case unittest for genesis.go?