* Optimize Pricefeed EndBlocker (#1851)
* optimize pricefeed endblocker to iterate all markets only once to remove
overhead of opening and closing iterator for each market individually.
In addition, extend tests to cover 100% of abci and price updating
behavior.
* use test cases that can't be confused with mean to ensure median is
always used
* update kvtool to master branch
* update changelog
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Co-authored-by: Nick DeLuca <nickdeluca08@gmail.com>