[HotFix] fix to charge gas cost for the key length in wasm execution

[yun-yeo]

Summary of changes

fix - cosmos/cosmos-sdk#10243

This update makes gas KVStore to charge gas cost for the key length to prevent cheap store operation from the contract.
This also requires softfork.

Softfork Schedule

	columbus-5	bombay-12
Height	6,470,000	7,800,000
Expected Time	2022-02-13T15:00:00 (UTC)	2022-02-11T15:00:00 (UTC)

Report of required housekeeping

• Github issue OR spec proposal link
• Wrote tests
• Updated API documentation (client/lcd/swagger-ui/swagger.yaml)
• Added a relevant changelog entry: clog add [section] [stanza] [message]

---

(FOR ADMIN) Before merging

• Added appropriate labels to PR
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)
• Confirm added tests are consistent with the intended behavior of changes
• Ensure all tests pass

[codecov]

Codecov Report

Merging #674 (bd59bd0) into main (f6a968a) will increase coverage by 0.41%.
The diff coverage is 93.65%.

@@            Coverage Diff             @@
##             main     #674      +/-   ##
==========================================
+ Coverage   45.03%   45.44%   +0.41%     
==========================================
  Files         120      121       +1     
  Lines        7001     7061      +60     
==========================================
+ Hits         3153     3209      +56     
- Misses       3601     3605       +4     
  Partials      247      247              

Impacted Files	Coverage Δ
x/wasm/types/gas_store.go	93.33% <93.33%> (ø)
x/wasm/keeper/contract.go	79.84% <100.00%> (ø)