Migrate state to store/v2

[roysc]

Summary

Implement a procedure to migrate state storage to the SMT-based store for ADR-040.

Problem Definition

As the new state store is implemented for ADR-040, we will need a command to migrate app state to the new store. Steps involved:

• iterate over all store keys and save them (without Cache layer) to store/v2
• send an IBC UpgradeClient request with the new client state

Proposal

• Implement an app command which is to be manually run on an offline chain.
• Upon next running the chain, the UpgradeClient event is emitted.
• The original database contents are not deleted or modified until the migration successfully completes.
  • Deletion could be left to an additional manual command.
• TODO: additional steps or considerations?

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For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned

[i-norden]

Closing as this is a duplicate of #10803, I moved any details here that are missing there over.