chore: caching paramset

[egonspace]

Description

We found that cachekv.mutex had a performance degradation.
We need to replace this mutex with RWMutex, but by caching the object in ParamSet before that, we can reduce the mutex contention that occurs frequently in cachekv.Get() calls.

I measured performance improvements of 1845 -> 1895 tps based on single remote node after this modification.

closes: #XXXX

---

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 #198 (0c78434) into v2/develop (623dd8c) will increase coverage by 0.05%.
The diff coverage is 76.19%.

@@              Coverage Diff               @@
##           v2/develop     #198      +/-   ##
==============================================
+ Coverage       53.46%   53.51%   +0.05%     
==============================================
  Files             653      653              
  Lines           47289    47384      +95     
==============================================
+ Hits            25284    25359      +75     
- Misses          19155    19170      +15     
- Partials         2850     2855       +5     

Impacted Files	Coverage Δ
simapp/app.go	83.79% <ø> (ø)
x/auth/keeper/keeper.go	48.61% <ø> (ø)
x/bank/keeper/keeper.go	75.00% <ø> (ø)
x/bank/keeper/send.go	85.08% <ø> (ø)
x/crisis/keeper/keeper.go	86.20% <ø> (ø)
x/distribution/keeper/keeper.go	81.57% <ø> (ø)
x/ibc/applications/transfer/keeper/keeper.go	83.33% <ø> (ø)
x/ibc/core/02-client/keeper/keeper.go	83.64% <ø> (ø)
x/ibc/core/keeper/keeper.go	81.25% <ø> (ø)
x/mint/keeper/keeper.go	64.51% <ø> (ø)
... and 18 more

[wetcod]

LGTM

[whylee259]

Looks nice!