[Feature] WASM oracle querier

[yun-yeo]

Summary of changes

• Add oracle wasm query interface

It will allow a contract to query exchange rates with any pairs of base/quote denom.

{
   "base_denom": "uusd",
   "quote_denoms": ["uluna", "ukrw",...],
}

Response and query interface can be found https://github.com/terra-project/terra-cosmwasm-bindings

close #404

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 #405 into develop will increase coverage by 1.52%.
The diff coverage is 88.46%.

@@             Coverage Diff             @@
##           develop     #405      +/-   ##
===========================================
+ Coverage    66.19%   67.72%   +1.52%     
===========================================
  Files          116      117       +1     
  Lines         5887     5035     -852     
===========================================
- Hits          3897     3410     -487     
+ Misses        1771     1414     -357     
+ Partials       219      211       -8     

Impacted Files	Coverage Δ
x/wasm/internal/types/query_binding.go	0.00% <ø> (ø)
x/oracle/wasm/interface.go	87.50% <87.50%> (ø)
app/app.go	92.00% <100.00%> (+4.56%)	⬆️
x/wasm/internal/keeper/test_utils.go	91.21% <100.00%> (+0.22%)	⬆️
x/wasm/internal/keeper/connector.go	47.82% <0.00%> (-9.32%)	⬇️
x/oracle/internal/types/hash.go	54.92% <0.00%> (-7.18%)	⬇️
x/oracle/internal/types/genesis.go	59.25% <0.00%> (-5.26%)	⬇️
x/market/genesis.go	75.00% <0.00%> (-5.00%)	⬇️
x/wasm/genesis.go	70.73% <0.00%> (-4.78%)	⬇️
x/oracle/internal/keeper/reward.go	70.00% <0.00%> (-3.92%)	⬇️
... and 111 more