perf: fix to use easyjson instead of amino when marshal abci logs

[wetcod]

Description

I found a bottleneck in runMsgs, the process of converting the Result.Log to a string.
( https://github.com/line/lbm-sdk/blob/v2/develop/baseapp/baseapp.go#L767 )
When marshaling Result.Log with JSON, it takes a long time because many reflects are generated by amino codec.
Since Result.Log is not registered in amino codec as RegisterConcrete, it has the same format as json.
So, instead of using reflects, change it to use the MarshalJSON function created with easyjson.
(In the case of the types registered in amino codec with RegisterConcrete, easyjson must not be used.)

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AS-IS

TO-BE

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• 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 #208 (2862b47) into v2/develop (88ab1bd) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@              Coverage Diff               @@
##           v2/develop     #208      +/-   ##
==============================================
- Coverage       53.49%   53.48%   -0.01%     
==============================================
  Files             653      652       -1     
  Lines           47376    47345      -31     
==============================================
- Hits            25343    25324      -19     
+ Misses          19178    19167      -11     
+ Partials         2855     2854       -1     

Impacted Files	Coverage Δ
baseapp/baseapp.go	77.94% <ø> (+0.85%)	⬆️
simapp/app.go	83.96% <ø> (+0.16%)	⬆️
store/cache/cache.go	88.88% <ø> (+0.65%)	⬆️
store/cachekv/store.go	91.34% <ø> (+4.21%)	⬆️
store/iavl/store.go	66.36% <ø> (+0.29%)	⬆️
store/rootmulti/store.go	65.25% <ø> (-0.72%)	⬇️
store/types/gas.go	75.00% <ø> (+1.82%)	⬆️
store/types/store.go	58.82% <ø> (-1.18%)	⬇️
types/context.go	96.15% <ø> (+1.21%)	⬆️
types/result.go	81.69% <ø> (-1.29%)	⬇️
... and 15 more

[egonspace]

LGTM