feat(historacle): Update proto messages and remove BlockNum from medians

[zarazan]

Description

• Remove BlockNum from median/medianDeviation.
• Only use the Historacle price proto message for genesis - otherwise use just a sdk.Dec object.
• Add medianDeviation to genesis
• Update medians from sdk.Dec to ExchangeRateTuple in GenesisState

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• confirmed the correct type prefix in the PR title
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[codecov-commenter]

Codecov Report

Merging #1588 (fcedd62) into main (1813b2e) will decrease coverage by 0.09%.
The diff coverage is 82.05%.

@@            Coverage Diff             @@
##             main    #1588      +/-   ##
==========================================
- Coverage   55.33%   55.24%   -0.10%     
==========================================
  Files          66       66              
  Lines        6636     6629       -7     
==========================================
- Hits         3672     3662      -10     
- Misses       2691     2693       +2     
- Partials      273      274       +1     

Impacted Files	Coverage Δ
x/leverage/keeper/grpc_query.go	62.68% <0.00%> (-1.50%)	⬇️
x/oracle/types/keys.go	60.00% <0.00%> (ø)
x/oracle/keeper/historic_price.go	93.40% <92.59%> (-0.54%)	⬇️
x/leverage/keeper/keeper.go	66.41% <100.00%> (+0.12%)	⬆️