feat: use fastcache

[egonspace]

Description

• apply fastcache to inter block cache
• apply fastcache to iavl nodedb cache
• add metrics for these caches
• add config for these caches

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 #164 (882318d) into v2/develop (31fab61) will increase coverage by 0.03%.
The diff coverage is 68.18%.

@@              Coverage Diff               @@
##           v2/develop     #164      +/-   ##
==============================================
+ Coverage       23.36%   23.39%   +0.03%     
==============================================
  Files             763      763              
  Lines          125110   125164      +54     
==============================================
+ Hits            29234    29287      +53     
+ Misses          92035    92029       -6     
- Partials         3841     3848       +7     

Impacted Files	Coverage Δ
baseapp/options.go	59.74% <0.00%> (-4.15%)	⬇️
server/config/toml.go	18.18% <ø> (ø)
store/types/store.go	60.00% <ø> (ø)
x/bank/keeper/msg_server.go	2.12% <ø> (ø)
store/iavl/store.go	66.82% <37.50%> (-4.10%)	⬇️
server/mock/store.go	25.53% <50.00%> (+1.08%)	⬆️
simapp/simd/cmd/root.go	80.64% <50.00%> (+19.16%)	⬆️
store/rootmulti/store.go	65.97% <75.00%> (-0.08%)	⬇️
store/cache/cache.go	87.50% <86.66%> (+0.40%)	⬆️
server/config/config.go	41.75% <100.00%> (+1.30%)	⬆️
... and 3 more

[wetcod]

LGTM