Cosmos gas multiplier params

[Kbhat1]

Describe your changes and provide context

• Add Cosmos gas multiplier numerator and denominator as param instead of hardcoded
• Corresponding sei-chain PR: Cosmos gas multiplier params sei-chain#1546
• NOTE: Adding more basic unit tests

Testing performed to validate your change

• Sei-chain + verified on local chain

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 44.04762% with 47 lines in your changes are missing coverage. Please review.

Project coverage is 55.34%. Comparing base (6f71ccb) to head (060b94d).

❗ Current head 060b94d differs from pull request most recent head d2fa137. Consider uploading reports for the commit d2fa137 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##            seiv2     #487      +/-   ##
==========================================
- Coverage   55.35%   55.34%   -0.02%     
==========================================
  Files         629      630       +1     
  Lines       53964    54046      +82     
==========================================
+ Hits        29873    29912      +39     
- Misses      21957    22000      +43     
  Partials     2134     2134              

Files	Coverage Δ
x/params/keeper/migrations.go	100.00% <100.00%> (ø)
x/params/module.go	57.14% <100.00%> (+1.82%)	⬆️
x/params/keeper/keeper.go	60.00% <88.88%> (+11.06%)	⬆️
x/params/types/genesis.go	0.00% <0.00%> (ø)
x/params/types/params.go	26.08% <52.17%> (+26.08%)	⬆️
x/params/client/cli/query.go	0.00% <0.00%> (ø)

... and 1 file with indirect coverage changes

[philipsu522]

thanks for adding migration logic - one thing i'd test locally too is migrating to a version with this change and verifying we have cosmosparams going fwd