Upgrade iavl and sdk with fast storage

[p0mvn]

Closes: #XXX

Background
This release introduces an upgrade of iavl and the SDK with fast storage implementation that represents a copy of the latest version of the tree with performance improvements. The fast storage nodes are indexed by key on disk as opposed to by hash with the original tree implementation. It allows us to preserve data locality for the latest state, significantly improving iterations and queries. This implementation introduces a negligible overhead for writes.

Downgrade-re-upgrade protection
We introduced a downgrade and re-upgrade protection where we guard for potential downgrades of iavl and the subsequent enablement of the fast storage again. This is done so by storing the metadata about the current version of the storage and the latest live state stored.

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For contributor use:

• Targeted PR against correct branch (see CONTRIBUTING.md)
• Updated relevant documentation (docs/) or specification (x/<module>/spec/)
• Added a relevant changelog entry to the Unreleased section in CHANGELOG.md
• Re-reviewed Files changed in the Github PR explorer

[codecov-commenter]

Codecov Report

❗ No coverage uploaded for pull request base (v6.x@c709aac). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             v6.x     #846   +/-   ##
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  Coverage        ?   19.06%           
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  Files           ?      167           
  Lines           ?    23684           
  Branches        ?        0           
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  Hits            ?     4516           
  Misses          ?    18387           
  Partials        ?      781           

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[ValarDragon]

Awesome!

[hleb-albau]

WOW